My march moves noticably at about 25-27 degrees, and it may well do at below 2... when it does it's like a switch.
My custom shops don't move.
Different light can cause issues but i think this is more to do with how the eye reacts to the available contrast. Hazy and bright or dark conditions reduce the eye's ability to determine focus.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep