OK, I'm back.
I removed and re-installed my cover several times. I did find a pattern where mine would fall off.
Here's what I found.
When looking at the cover (your head is over the engine and you're looking forward), the right hand tab hits the plastic cowling that's behind the seat. This is occurring near the bottom of the tab. If the entire length of that tab (all 3-4") isn't fully locked in, the cover easily falls off.
To resolve, I locked that right hand tab into place and assured the full tab is in place by visual inspection and sliding my finger down the right hand side between the back of the fuse panel and that plastic cowling for the seat to assure I have a full lock on the right side. I then locked in the left tab. It then stayed in place.
If this doesn't work for you, do the same thing but when done locking in both tabs, slide the fuse panel cover to the right to assure you have a good lock on the right side.
If it still doesn't work... Look at the sides of the fuse panel cover. If the 2 sides that have the tabs are bowed in, try to bend them out slightly. 2-guns knows more about this but the application of heat before bending, then holding those sides out until cooling may help to keep those sides bent outward more. By being bent outward more, once they lock in, you shouldn't have any issues.
Give it a try and let us know.
Brian