Can't delete or rename .mkv extension videos

When using Smart Mode and choosing .mkv as the extension for the videos to be saved as, the files will play ok, but I simply can't rename, delete or move then. Every time I try to perform one of those actions it hangs "thinking" until I click cancel.

I believe there's something to do with the explore.exe process, because the only way I can delete those files is to end all explorer.exe processes and use cmd command lines to manually remove them.

Ii has been happening for some 4K Downloader versions by now. I'm currently using 3.6.0.1760 (registered) and it still happens.