Sequoia won't write to USB sticks

Just setting up my new Mac Studio with Sequoia 15.3.2. Because the USB-A ports at the rear are dedicated to USB drive hubs, my only practical option are the USB-C ports on the front. I have old sticks for which I bought USB-A > USB-C adapters. Don't work...can't write to them. I can see them. I can read from them. I can copy from them. I ca even delete files on them. Just can't write to them (except on rare cases when it does happen, but I can't reproduce that). I even reformatted one (FAT32) and still can't write to them (2GB, nothing FAT32 can't handle). I thought is was Sequoia and/or my Mac Studio but just discovered that I can't write to them on my older 2019 iMac (Sonoma 14.4.1). I normally used sticks to copy from my scanner to my computer, can't say I ever recall writing to them.

Today I received two new sticks (Sandisk Dual Drive) that have USB-C on one end and USB-A on the other. They are equally wonky.

Found several posts online about Sequoia having issues with USB, but none like mine.

Can somebody corroborate what's going on?