To clarify, are you enabling the text gameObject or text component? There's a biiit of code that'll be changing in the next update that should finally make the two work exactly the same, but...
In some situations, when enabled, Super Text Mesh will actually take one extra frame to recalculate. It's an old fix to get around a problem with async loading. Using a manual Rebuild upon enable is probably the best option here. (You can disable auto-rebuild in the inspector to prevent it from rebuilding twice!)
Hopefully that works... if there's any further issues I'll take a deeper dive into this!
