Seems like I managed to resolve the RAM issue reseating them.
I’m still tweaking a few bios settings to get optimal performance out of the system - and realised my fans were running on DC instead of PWN so were much louder than desired.
Plan at the moment is to swap out some of the Corsair fans for quieter Noctua fans, and add the full number the case can support.
Will likely want to add more storage at some point as well - got quite a few M.2 slots available for use.