Bug: Underline Whole Paragraph

Thanks for the reply. I uninstalled and reinstalled Pages, but still have the problem. I did a screen recording to show what's going on. It is not consistent. I can place the cursor after the first letter of a word and use command-U to underline, and it will sometimes work correctly and sometimes do the whole paragraph. I've tried with both the built-in keyboard and two different external keyboards. Here's the video. In it you can see that the same words done at different points in time have different outcomes. This is driving me crazy. https://youtu.be/xjDjDW_a7ZQ

Viking, I took some more steps as suggested. I removed Clean My Mac (the only monitoring software I could think of). I booted in safe mode. I logged into the guest user account. I removed and reinstalled Pages. I launched Pages while holding the Shift key. In all of these scenarios, I'm having the same issue. If you have any other thoughts, please pass them on.