Pistons can take between 2 to 3 ticks to completely extend and retract when receiving a 1 tick pulse. This can effect many different creations and has to my knowledge existed for awhile. This means that sensitive or precise circuits circuits, Tflipflops, and flying machines to name a few can become much larger, slower or unreliable. A bug report has already been made mentioning this issue that is as yet unresolved however it did not go into detail of the problem.
Wrong project, you inserted this bugpost in Java Edition.
Piston timings are apparently currently random in Bedrock, not in Java Edition though.