Oh that's a relief to hear actually... I was reviewing my to-do list and realized this was left unanswered, so... I actually went in and added some optimization to the OnRectTransformDimensionsChanged() callback over the weekend. So now it only calls Rebuild() when it absolutely needs to (much less intensive to check for this change than just go through with it, turns out...) and I added a toggle to completely disable the callback in case this situation arises again. (Or I guess Remember Read Position can be left unchecked now if this extra boolean is enabled!)
That should be out in the next update, just making sure other fixes work before publishing it.
Additionally, since we last talked, an update came out that allows Unity's "Outline" component to be used with STM with the new STMMaskableGraphic component, and the Ultra shader is even better now! (One bugfix for the Ultra shader is in the next update coming out, but you'll get 100 points if you manage to figure out the condition that causes the bug I fixed to appear in the first place)