Xdelta3 Child process stays active after application closed

[thygrrr]

Version 1.5.1 OS: Windows 11 Professional

When the application hangs or seems to hang (trying to make patches for very large TAR files), the application makes no visible indication of any progress happening. (this is a minor UX issue, and somewhat understandable when the workload is just 1 item).

However, stopping and starting the application leaves whatever work was being done at the time in a bad state.

Faulty behaviour: Closing the application leaves the output directory locked by a still working Xdelta3 process. (workaround is to unlock the directory by killing the process, e.g. via File Locksmith, or just the task manager)

Exacerbation: It's very hard to tell that the application is still working (other than by looking for the process in task manager. Only the greyed-out Go! button seems to be a hint, but all of the remaining UI still appears fully interactive.

Expected behaviour: Child processes should be reliably terminated on application quit via Alt-F4 or close button.

Suggested UX addition: Change the progress bar's range by adding 1 to the item count; only finishing the last step and fully filling the bar when the final sub-process returns.

[thygrrr]

There also appears to be a warning in the form of a .bat (?!) file in the output directory.