RStudio miserably slow on OS Monterey when knitting xaringan-slides

I am having problems with VERY slow displays of my xaringan slides on two of my Macs (one is a 2017 iMac Pro macOS Monterey Version 12.4 with 128 GB RAM the other is a M1 Max MBP with 64 GB RAM) but the third one (which is an 2018 MBP running Big Sur Version 11.6.4 ) is performing like normal. The slides knit like normal but when the window to display the slides renders it stays blank for about 50-60 seconds instead of the 0-5 it normally takes. I rolled my new machines back to RStudio 2021.09.1 Build 372 and Xaringan 0.23 to match the old machine and the performance is still a mess. Once in a while the new machines render properly but at least 90% of the time they are aweful. Moonreader is basically not usable on the new machines. I think this is exactly the same problem that cathblatt reported in another locked help posting. Any suggestions?