In this case of a simple recurring Issue i agree with showing a CM how to put the cover back. But let's look at it from this angle, suppose it was acceptable to fix it yourself and you have a cast member that feels intimidated that their job maybe on the line if they don't get in there and do the task when they know in their heart it's beyond their capabilities. Now you just put them in a bad spot and back to safety what if they hurt themselves in the process. A workers comp. Insurance guy is going to ask why did that person touch that? Is that their job? Was he trained to do that? It just opens a Pandora's box of issues. I don't disagree with your line of reasoning I'm just looking at this from different angles. In my previous line of work I got caught up in a few issues that I happen to witness. When you get to court the lawyers are like off the hook tearing up people's testimony.It seems like some common sense could be involved like:
If the cover falls down, push it back up (here's how) and clip it into place. If it's a recurring issue, report it to maintenance.
Please don't fix the AC system in the Monorail nor change its tires nor repair doors nor try to separate the cars from the train.
I think the problem is that people want to draw a line in the sand which, again, stops your employees from thinking. If you have good employees they should be smart enough to know when/where to stop and you don't really need to define that line, if they do try to help but end up going too far then you tell them, "Thanks for trying but let's let maintenance handle that next time."