What I’ve noticed is if I use # for H3 and H4 etc inside the Scribe stack then activate the floating image child, then "add a caption’ the caption when published appears as a header and in bold. If there isn’t any headers in the text area of Scribe then it displays as text and not automatically bold.
If you can find the cause then try and post a url to a test page for me to see. I’m about to pack up my computer this morning and the removals men are about to arrive. I will therefore only be able to look on mobile or my laptop when I get a chance.
If it is being made into a header in the HTML then that is happening via the RW markdown processor and we need to find out why.
I suspect it is more likely to be some CSS though as a first guess.