I'm too new to over really useful advice. but I suspect the relevant portion will be here
13:58:15.719: ==== Recording Start ===============================================
13:58:15.719: [ffmpeg muxer: 'simple_file_output'] Writing file 'C:/Users/tiger/Videos/Physics Lecture/2020-09-23 13-58-15.mp4'...
13:58:38.024: output simple_file_output paused
14:00:52.801: output simple_file_output unpaused
17:03:08.591: output simple_file_output paused
17:03:28.566: output simple_file_output unpaused
18:06:21.149: [ffmpeg muxer: 'simple_file_output'] Output of file 'C:/Users/tiger/Videos/Physics Lecture/2020-09-23 13-58-15.mp4' stopped
18:06:21.149: Output 'simple_file_output': stopping
18:06:21.149: Output 'simple_file_output': Total frames output: 573433
18:06:21.149: Output 'simple_file_output': Total drawn frames: 524635 (893125 attempted)
18:06:21.149: Output 'simple_file_output': Number of lagged frames due to rendering lag/stalls: 368490 (41.3%)
18:06:21.150: ==== Recording Stop ================================================
18:06:33.691: Video stopped, number of skipped frames due to encoding lag: 574516/582220 (98.7%)
I recommend searching this forum on recommendations against EVER recording using MP4
And that lag would seem to indicate (to me, who doesn't know enough to be authoritative on this) that the PC (CPU is overloaded)
Also I see different audio refresh rates, so some OBS optimizations may help?
I had a 5yr gaming laptop with an i5-6300HQ (lower end than what you have) and GTX 960M and my live streaming (PPT and a webcam), and a variety of format pre-recorded videos, overwhelmed the PC
Hopefully someone much more knowledgeable than I will assist you. In the interim, I suggest figuring out how to check PC resource utilization using Win10's native Task Mgr (Performance) and/or Resource Monitor
