Might be related to… How do I stop TipTap adding p tags to my li items? - #2 by mistyn8
Have you tried
<ul class="steps">
<li class="step step-primary"><p>Register</p></li>
<li class="step step-primary"><p>Choose plan</p></li>
<li class="step"><p>Purchase</p></li>
<li class="step"><p>Receive Product</p></li>
</ul>
It might leave it alone then if it sees the <p/> it wants?