Unity-created animations loop delay problem

I created some animations in Unity 1.x in 2007. The current version of Unity doesn’t seem to like them. Seemingly at random, extra time after the final keyframe is being interjected, resulting in inability to have clean loops. Do you know why, or how to erase it? Every time I restart the project, Unity seems to be interpreting the loop point differently. This is the case with all of the animation clips (about ten).

I’ve come across a couple threads that seem related. Here’s one:

I didn’t find any fixes yet.

Bump before bug report.

I also have this problem… does anyone know the answer?