7i76E spindle encoder - strange readouts

If you want to test the speed: print a high slot wheel. Connect to a speed regulated drill and augment the speed til you see unregularities on halscope. Do that on all three of them. So you might see a flaw in one ofthem or that you are near the led's speed limits.
Mike

Finally I printed new wheels 24ppr and all works fine now. Optocouplers which I used stops working over 3kHz.

Good solution