Captivate 2017 - Repeatedly encountering "corrupted" Fluid Boxes

Hello,

I'm repeatedly encountering an issue where Captivate seems to insert additional, oversized fluid boxes into my layouts that cannot be deleted. Although they can be 'selected' on the the slide, they don't appear at all in the "fluid box selector" window. Resetting the slide masterdoesn't remove them and the only I thing I can do is delete the slide and start all over again!

Truthfully, I've encountered various forms of 'corrupted' fluid boxes almost constantly since I started trying to work with 2017 - very often having to reset the slide and reformat or replace text/images/shapes repeatedly. I've been through the forums, but no one else appears to be reporting these issues. For what it's worth, I've been trying to use fluid box layouts on the master slides where possible.

To say that making fluid boxes a workable solution in Captivate has been a struggle is an understatement. I'm well aware of their limitations and have begrudgingly accepted these, but the project now seems so fundamentally unstable and buggy that I'm about ready to throw in the towel. Can anyone help?