What is H.264 Main L.5? How do I convert this to a lower profile so I can use it as a medium H.264?

Alright, so I made one of my first videos through Davinci Resolve 17, but I used stock footage from artgrid.io, the resolution is extra high and every time I try to render it I have a failed playback issue, and when I ignore the messed up frames I still have a lot of glitching"Media offline" frames. I do not have a H.265, I've tried EVERYTHING to somehow fix the issue but nothing has worked until now (rendering 1 frame a second, getting rid of cache, using "smart" cache, turning off all decoding options and etc., this video surprisingly has everything that hasn't worked so far [https://www.youtube.com/watch?v=BzDN91GmaSs&t=118s](https://www.youtube.com/watch?v=BzDN91GmaSs&t=118s))

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I think after I'm able to convert these videos (20-30) into medium (h.264 l.4) profile vids then I'll be able to use it properly on DaVinci without that annoying media offline frame. I don't much about ffmeg, or if that could help me with converting the l.5 to l.4. I NEED HELP!

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Computer specs:

Dell Optiplex 7040

Intel core i7

16gb ddr4 ram

Intel 530 Graphics card