So i was doing a run and when I got to lv10, I never got the correct level gear out of weapon vendors, but shield and ammo vendors were all on level. I also ran into a glitch where every time i would interact with Marcus, it would play the intro cutscene even if it had already played. Do you know what could have caused these glitches and how to solve them if they happen again?

the marcus cutscene plays everytime if you don't take the "rock paper genocide" quest, also why are you going to marcus in a speedrun?

I had a similar issue. I've run the game multiple times before and I didn't travel to sanctuary after flame of the firehawk until level 10 but the vendors were still level 9. I'll put a link to the relevant parts (if more of the stream is needed let me know).