[DavidPP]

I have the exact same issue, it's driving me crazy. I'm wondering where the issue lie as my partner as the same setup (same version of macbook air/same monitor) and doesn't seem to suffer from that issue.

The biggest difference is that I updated while he did a clean install.

[frenger]

I think clean install must be the answer tbh - I upgraded too. I'll let you know if I try it, maybe over the weekend.