Sorry, the program has actually gone troppo. Recent Files has a file listed. The file is NOT open. None of the options will remove the file from the list. Cleanup will not remove it (thus presumably this is why AxCrypt wont close).
Task Manager has File Encryption using 97% of CPU (Background Process).
Task Manager closed File Encryption. Opened file again, AxCrypt restarts OK. File Encryption in Apps list this time. Closed file. Can exit AxCrypt OK now.