Thank you for your email.
I use “Task Manager” to make sure the files are not open and close any that are.
I am guessing that it is a win 10 system file such as “Film & TV” that cannot be closed easily where the file may still be open. But this is a guess only.
One would have thought that the Axcrypt would take this into account. I was going to get the Premium version but this is becoming so annoying I am not certain anymore.