Multi Response question

I took a look at your file, and I noticed when I looked at the Format Shape settings, it had "Resize shape to fit text" and "Wrap text". Unfortunately, no matter what I tried to do, those settings were grayed out, and I couldn't edit them. I created a new Multiple Response slide and checked the settings to see if they were the same, but the new slide had "Shrink text on overflow" and "Wrap text" checked instead. Again, I couldn't edit these settings for whatever reason, but with those settings checked, the fixed-height issue did not happen. You might just have to recreate the Multiple Response slide from scratch.