I am having exactly the same problem that was described at the beginning of this thread. Like many of you, I have been using Shortcut very successfully for years on my current hardware - but I have never seen odd performance problems with the UI until now.
My i7-5820k (6 cores, 12 threads clocked at 3.3GHZ), 32GB, with 24TB of 7200rpm disk storage (with distributed paging files across all spinning disk drives), Windows system recently upgraded itself from 10 Pro to 11 Pro around the same time Shortcut was upgraded to the most current version (22.10.25). I have seen no adverse reactions whatsoever from any other applications, including many heavy duty games under Windows 11.
In Shortcut once I try to load an input video file, the Shortcut UI’s performance becomes so sluggish that it is practically unusable - often taking 2 or 3 minutes between each fairly trivial interaction with the UI In the Task Manager I see “melt.exe” consuming 60% to 90% of the CPU resources, using a couple of gigabytes of memory, and doing 3 to 4 MB/s of disk activity. I think it’s doing this even before I have created any background job to process the input files.
I’ve tried turning the hardware encoder on and off and de-installing/re-installing Shortcut with no effect. I’m not sure if the particular input files (created by a standalone hardware encoder or a commercial video editing program, “PowerDirector” that I used to use which are usually quite a bit larger than the files I create with Shortcut) may be triggering the problem too. The input files I’ve been seeing these problems with recently are are roughly 4 to 15GB in size. It should also be noted that even when the Shortcut UI is being very, very unresponsive, any other application I bounce back to on the desktop is running fine, with no performance issues at all.
I’ll keep playing with it to see if I can figure anything out that effects this problem, but when this problem is occurring - it makes using Shortcut totally painful! Thanks in advance for any further thoughts or suggestions!