Have reduced file sizes to about 165Kb although they were smaller than 8Mb in the first place. Same result. Have tried sending you a message by WeTransfer but don't know if you will get it. Let me know. Don't use Dropbox.
Michael, I had no problems inserting the screenshots you sent me, so try a different web browser the next time, or copy and paste images into the reply box.
I don't know what's causing this, although I vaguely remember having seen posts about the same problem before.
But I suggest that you first of all make sure that your graphics driver is up to date.
If updating the graphics diver doesn't help, try do disable the GPU in ACR and/or Photoshop.
In Photoshop, press Ctrl+K to bring up preferences, and uncheck Use graphics processor in the Performance tab.
In ACR, also press Ctrl+K to bring up preferences, and uncheck Use graphics processor at the bottom.

