I've been experiencing this occasionally ever since I started using guix. It happens on all of my machines and across different setups.
I don't use syncthing so it's probably not that. The set of services I have has changed so much I'd have trouble identifying a singular service that was in all of the instances of this occurring save for those in %desktop-services. iirc I once managed to get a debugger out when it happened and it's stuck waiting in one of the epoll/select/alike calls, sadly don't remember exactly which one. Will investigate next time it happens. The only remedy I know is indeed SysRq. So that's at least 4 people now
