Any tips on improving spin number accuracy/consistency?

I’m registering “correct” (i.e., reasonable) spin numbers maybe every 5th shot. For example, several 7 irons will be in the 2,000-3,500 range and then I’ll have one register at 6,000. Then back to the 2-3k range. Same across the bag. I’ve tried using different balls (including TP5x pix to see if the graphics help) adding/removing lighting without luck. Grateful for any suggestions. Hard to have faith in the other numbers when you know spin is off by 2x.