FaceTime on iPad Randomly Resizes Screen During Call with One Person

During video calls with one person, FaceTime starts out full screen. However, after a number of minutes, the screen shrinks to about 1/4th scale. Sometimes, it pops back to full screen for a moment or two, but then shrinks back to a small screen. I’ve tried changing numerous settings, but nothing works. Looks like it’s a bug with the iPad only. Does anyone have a solution?