Disable and enable Next button triggers still controlling slide after the triggers are deleted

This is an issue that I've had for several years now, in different courses, different computers, different installations. I'm hoping it's me!

When a client requests that I lock navigation somehow, for each slide, I will create a trigger that will disable the Next button when the timeline begins and enable it when the timeline ends. Works as advertised.

Later on, perhaps weeks, maybe months, I revisit the course and decide to remove those triggers for whatever reason. I highlight them and delete them on each slide. Again, works as advertised.

BUT, when I preview or publish the slide/course, the Next button still behaves as if the triggers are present. The Next button becomes disabled and won't enable until the timeline ends. I have tried to remove and re-add the buttons. I have removed and re-added the "Jump to slide" triggers. They don't behave corrupted in other ways.

I've tested it to see if I remove the triggers 5 or so minutes later will the slides behave as expected. They do. I don't know whether this happens to all my courses that are restricted. It happens enough to annoy me.

Update: I just copied the course into a new file and the course is behaving as expected. Is this a corruption issue? But so many different computers, files, and installations? I don't know. I'd hate to have to paste my courses into new files all the time.

Has anyone else seen this?