Screen sharing on second monitor (ipad) problem

Normally I have zoom lessons with my students. And I will do screen mirroring with iPad (as second monitor) from my macbook pro M1. Everything is as normal until two weeks ago, my student said he saw the shared screen is keep flashing. At the beginning, i thought it was my students problem. However, until these days, more students have the same problem with my shared screen. I am frustrated about that because the shared screened shown in my ipad is completely normal and no flashing at all. And I test with my students, once i moved back my shared screen to my macbook pro (main display), they said it's normal and no flashing but flashing again when i move my shared screen to ipad (second monitor). Please kindly advice. Im exhausted about this... Thank you very much.