FFS freezes when moving scroll bar

[ebirdman]

I encountered this problem starting with 9.6 version and the same is with the latest.
System: Windows 10, 16GB RAM, 256GB SSD
Trying to sync between local drive folders and USB flash drive according to FFS script configuration -
if I run "Comparison" (two-way synchronization) and then do not change the shown "changed on both sides", everything works even if I move the slide bar. Also everything works if I do change "changed on both sides" status to "move to the right" backup drive (USB drive) on a 150MB file but do not try to slide a vertical bar.

But only if I change the status of the file from "changed on both sides" to "move to the right destination" and then try to move vertical slide bar down, it will freeze half way down and then application becomes unresponsive. At the system level I still can close FFS but nothing can be done within FFS window. I rebooted the system, repeated different sequences but it repeats the same phenomenon in the same sequence.
Is it a bug?

[Zenju]

Interesting! Can you send me a crash dump file using FreeFileSync 9.9 when it hangs?
https://freefilesync.org/faq.php#crash

[FreakAzoiyd]

I have a similiar bug it persists since a couple of version (my estimate would be half a year up to a year).
I just snyced the folder overall containing 49k files and thus can't reproduce it right now. When it occurs next time I'll send you the dump.
When I scroll the changed/new item list it hangs at about position 650 where a huge block of solely new items appears. It seems that only the new items cause this error.

[Zenju]

Are both of you able to reproduce the hang? I have some idea what is going on and would like to create a test version.

@ebirdman: To help you reproduce:
according to your dump file, the hang occurs once you scroll to a file with the extension "wmv".

[Zenju]

Here's the fixed version: http://www.mediafire.com/file/ex2bw6gqvgcideb/FreeFileSync_10.1_%5BBeta%5D_Windows_Setup.exe