How can you make file deletions stick with a folder sync?

I use SyncBack to synchronize some of my media files to a home theater PC. The sync needs to go both ways because sometimes new files are created on the HTPC and need to go back to my main PC, and sometimes it's the other way around.

The issue I'm running into is that when I delete a file (which typically happens on my main PC), the next day it will just copy back over from the HTPC. It seems like there should be some way for me to avoid this behavior without requiring that I manually delete the file from both locations. At first, I tried to set a Profile that would delete files that only exist on one side if they hadn't been modified in the last day. That almost works, but sometimes downloaded files or files extracted from an archive will show a "modified on" date from sometime far in the past, even though the "created on" date is in the last day.

I've been scratching my head about this for a while, because this should be easy to solve, since I couldn't find any other posts about it (here or elsewhere), and it seems like an issue anybody with synchronized folders would run into. Am I missing something obvious?

Thanks in advance for any and all suggestions!