I have 3 cameras. 2 work great and the garage camera continues to record like this
This is bitstream corruption/loss.
Try swapping the camera with one that works, and see if the problem is linked to the camera or the location,
Could this be related to poor wifi strength? It’s a bit far from the house.
Absolutely. If that's the case, when you swap the cameras the one in this location will still have corruption.
Directly to my home wifi. Which is in the house and this is on the garage approx 75ft away. It worked before
That is a long way though. You can of course try using your phone in the garage (with mobile data turned off), and see how well the wifi works there.
If the garage is powered from a breaker panel in your house, you could also use a powerline kit to get wifi to the garage. You'd connect ethernet to a powerline adapter in your house, then then plug in a powerline/wifi combo in the garage. Performance does depend on details of the circuit, so this could be hit-or-miss. But something like this: https://www.netgear.com/home/wired/powerline/plw1010/