What does the dotted line mean, and do I need to worry about it? I think it has something to do with frame boundaries not matching, but how could that happen if I have quantize to frames on? Wouldn't Vegas make edits and text events precisely on frame boundaries?

For the type of videos I create, which are game play videos, usually of pinball games or bagatelle games, I shoot the videos and chop them into pieces for each game played. The problem arises when I introduce the text / animated text events to each seperate clip. Sometimes it appears at the beginning of a clip, sometimes at the end, sometimes on both ends (I think).

When I see this at the end of the section, I just back up one frame and snip off the last frame, then it goes away. However if I do this at the beginning, it messes up the start of animated text events, which I use a lot. Do I need to do anything when I see this?

I'm doing these videos as a hobby, nothing professional about them.

Any insight would be appreciated. Thanks.

Edit to add: In the screenshot, the middle event appears to be off centered from the rest, but it's because that event is slightly shorter than the rest and includes another event immediately after that one.