N64 turns on, audio works fine, but video cuts in and out?

[/n64]

Hi all, hoping i can get some help here. Recently got a receiver to use for some audio stuff and unifying my consoles and discovered it had AV on it, dug out my N64, game cube, and ps2 and plugged them in but the N64's video doesn't work at all.
It keeps looking like its trying to fit to a certain aspect ratio or something, it just flickers in and out rapidly. Now i tested using the same AV cable on the game cube as i only have the 1 and it works fine, and the ps2's av cable works fine for it too.
Any ideas as to what could be wrong with it? any help is appreciated.
EDIT: Solved it! its the amp/receiver i have, it works fine on my old tv (just a 1080p flatscreen) but on my 4k through the amp it causes the weird flickering!

submitted by /u/Falconmcfalconface
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