I have a really weird problem, I have a particular program installed on several machines. On one machine when the Alt key is pressed whilst in this program, if it is released without pressing another key with it (i.e. tab, F to open the file menu etc) it will lock the program until I end the task in taskman. I can switch to another Window e.g. Excel (can't use alt-tab though) and the machine works fine but the Alt key will not work on any other window until the crashed program is quit.

This only happens on one machine out of all of them.
When pressing the Alt key in this program the top menu is correctly highlighted, as long as I hold Alt down I can press F and the file menu will open correctly after which I can release both keys and it does not crash.
Same in Safe Mode.
Same after clean installing the OS.
All other programs work fine when pressing just the Alt key.
I have swapped out the RAM just in case - same.
I swapped the drive (m.2 SSD) into an identical machine, the issue follows the drive i.e. the working drive in the problematic machine is fine.
I have clean removed the software and reinstalled - same.
When it crashes I cannot use shortcuts such as Win+X until I close the program.

Any ideas? It must be software as I can't see a problem with the SSD causing this on just one program.

It may be unrelated but occasionally Excel will have an issue whereby the File menu goes blank, the buttons are still there and usable. I have disabled hardware acceleration in Excel to test this and updated the GPU drivers.