### Which Umbraco version are you using? (Please write the *exact* version, exam…ple: 10.1.0)
15.2.1
### Bug summary
**Accordion BlockList**
**Accordion BlockList Item**
**Error on saving**
**Error Log**
System.Text.Json.JsonException: 'C' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
---> System.Text.Json.JsonReaderException: 'C' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)
--- End of inner exception stack trace ---
at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)
at System.Text.Json.JsonSerializer.ReadFromSpan[TValue](ReadOnlySpan`1 json, JsonTypeInfo`1 jsonTypeInfo)
at Umbraco.Cms.Infrastructure.Serialization.SystemTextJsonSerializerBase.Deserialize[T](String input)
at Umbraco.Cms.Core.Models.Blocks.BlockEditorDataConverter`2.Deserialize(String json)
at Umbraco.Cms.Core.PropertyEditors.BlockValuePropertyValueEditorBase`2.CleanupVariantValues(List`1 sourceBlockItems, List`1 targetBlockItems, Boolean canUpdateInvariantData, HashSet`1 allowedCultures)
at Umbraco.Cms.Core.PropertyEditors.BlockValuePropertyValueEditorBase`2.MergeVariantInvariantPropertyValueTyped(BlockEditorData`2 source, BlockEditorData`2 target, Boolean canUpdateInvariantData, HashSet`1 allowedCultures)
at Umbraco.Cms.Core.PropertyEditors.BlockValuePropertyValueEditorBase`2.MergeVariantInvariantPropertyValue(Object sourceValue, Object targetValue, Boolean canUpdateInvariantData, HashSet`1 allowedCultures)
at Umbraco.Cms.Core.PropertyEditors.BlockListPropertyEditor.MergeVariantInvariantPropertyValue(Object sourceValue, Object targetValue, Boolean canUpdateInvariantData, HashSet`1 allowedCultures)
at Umbraco.Cms.Core.Services.ContentEditingService.EnsureOnlyAllowedFieldsAreUpdated(IContent contentWithPotentialUnallowedChanges, Guid userKey)
at Umbraco.Cms.Core.Services.ContentEditingService.UpdateAsync(Guid key, ContentUpdateModel updateModel, Guid userKey)
at Umbraco.Cms.Api.Management.Controllers.Document.UpdateDocumentController.<>c__DisplayClass4_0.<<Update>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Umbraco.Cms.Api.Management.Controllers.Document.UpdateDocumentControllerBase.HandleRequest(Guid id, UpdateDocumentRequestModel requestModel, Func`1 authorizedHandler)
at Umbraco.Cms.Api.Management.Controllers.Document.UpdateDocumentController.Update(CancellationToken cancellationToken, Guid id, UpdateDocumentRequestModel requestModel)
at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(ActionContext actionContext, IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
at Umbraco.Cms.Web.Common.Middleware.BasicAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Umbraco.Cms.Api.Management.Middleware.BackOfficeExternalLoginProviderErrorMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
at StackExchange.Profiling.MiniProfilerMiddleware.Invoke(HttpContext context) in C:\projects\dotnet\src\MiniProfiler.AspNetCore\MiniProfilerMiddleware.cs:line 112
at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Umbraco.Cms.Web.Common.Middleware.PreviewAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestLoggingMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)
### Specifics
_No response_
### Steps to reproduce
https://github.com/user-attachments/assets/432e4f0f-62a1-4e86-9dc3-a1a4179f232a
**Json Payload**
[payload.json](https://github.com/user-attachments/files/18859478/payload.json)
### Expected result / actual result
Expected result is to save and publish the document without any error