OS will not mount the VM partition. Virtual memory must be forced to work
Solved. Cobbled together a workaround with information from interwebs.

Created this plist named “local.mountdisk1s4.plist” containing:





             Label
             local.mountdisk1s4.plist
             ProgramArguments
             
                  /sbin/mount_apfs
                  disk1s4
                  /private/var/vm
             
             KeepAlive
             
            SuccessfulExit
            
             



Placed it in /Library/launchdaemons

Swapping now works as it should. Still not sure how this all broke in the first place, or if there's a more elegant solution.