Problems opening Last opened/recent documents in Adobe Illustrator

I teach Adobe Illustrator to around 60 16 year olds.
When they first open the program & either double click on the image of their last document it often won't open. In fact it often opens another recent file, but not the one they actually have clicked on. The only way round I have found to get up their work is to >window & turn Application Frame off? This is far from ideal & I don't understand why it's suddenly started happening......
As you can imagine the 16 year olds find this confusing as one would assume double-clicking on an image of their document would open it.

I've noticed more & more weird glitches with Illustrator in the last year. Are you now implying old Microsoft coding geeks to complicate things????

Don't even get me started on the new tool bar shinanikins........

Disgruntled Adobe user since 2000