I did pick up a couple of SanDisk xPros.? Seemed the issue may have been the factory format - I zapped the 2nd on w/ xFat (not FAT32) and no hitch w/ Etcher.? So maybe that's the issue. Also on MacPro (yeah yeah I'm 25+ yrs *nix guy).? I dd'd the 1st SDCard (wiped block 0 & 100) and the PI imager did all the magic - so long story short - not really sure of the issue - but both 128Gb's running like a charm.? Now onto USB boot on Pi4....