Z690 Riptide single memory stick possible£

Hello dear forum members,

I've been running into a problem last morning with my Asrock Z690 Riptide and a Intel i7 12700k setup, getting lots of bluescreens with many different error codes, complete system freezes and the computer rarely "POSTing".

I'm assuming a memory error might be the reason this happened (currently, the PC is running again after a fresh Win 10 install on a new NVME with only 2 memory sticks inserted into the mainboard; had ONE freeze though), so now I've got to trace the problem and find out which modules - if any - are faulty.

As of now I only got the system starting with two modules inserted and I've already checked the manual, which is mentioning the dual channel population (page 17 in german language manual) but nothing regarding a start with only one RAM module inserted. Can the board boot with only one RAM slot populated? If so, which one might that be (I know they're labeled A1 & A2 and B1 & B2).

I'm also open for any troubleshooting suggestions. I will try running Memtest86 off a USB drive and see if it encounters any problems.

Thank you for reading and helping.