pixellation of image

[Clematis1]

Please could somebody help me. I have a problem with pixellation of image which happens every time I teach (hosting the meeting) now. My image is ok but the pixellation moves from one student to the other. This is in gallery setting

When I attend a zoom meeting its the Speaker who is pixellated and it only goes if I am on gallery setting (as opposed to when I host)

I have tried to get in contact with customer support but there only seems to be an American phone number (Im in the UK) This has been happening for over 6 months now. Its very inconvenient and I am very tempted to change from Zoom if it cannot be resolved.

Please could someone help!

Thank you