I'm getting out of memory crashes with 6.12.8 and had the same issue on 6.12.7-rc2. Unfortunately I haven't had time to dig deeper until now.
Syslog isn't reporting anything interesting but I've attached the diagnostics.
I think the issue is being caused by the web ui. I managed to get a couple of screenshots from htop just before the system crashed.
m33-nas-01-diagnostics-20240221-1244.zip