Here is a simple ~one click "program" to fix jerky play with borked mp4/mkv files, it doesn't do encoding, just remuxing.
It will fix only downloaded video streams (aka WEB). Use it only on the borked files!
It will generate & add chapters too.
For operation
it needs ~x2 free space (at the file's location) for what you're dropping on it.
Usage:
1) Place bat on Desktop or other place, Drag & Drop on it(on icon) the mkv or mp4 files you want to fix. Or usual way with command line: "JerkyWEBFixer video.mkv"
2) Enter selected FPS (press 1 or 2 or 3... and press Enter). If selected FPS is not as original (btw, some borked files shows some nonsense fps) then audio will be out of sync.
3) New mkv file will be generated with "_fixed" tailing.
Requirements:
Windows OS
MKVToolNix installation at the default path.