On my machine, if I enable either version of the new SMAA antialiasing options, the flashing squares go away. Not a fix, but maybe this work around would also work for you?
I’ve spent a bit of time looking into this. I wish I had more to report. I presume something sketchy is going, but it is subtle.
I’m seeing this on one of my machines with a different graphics card. At least it is not tied to one particular piece of hardware.
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