Just have similar problems. Foxlor seems to worked for a while, then error "Service Unavailable" and the socket /run/php/php7.3-fpm.sock was missing. Reinstalled FPM, the same happened again ... (I use Debian 9) (Iḿ just very new with foxlor and it seems a little bit tricky to run it)
Apache Error Log says:
[proxy_fcgi:error] AH01079: failed to make connection to backend: httpd-UDS
[proxy:error] (2)No such file or directory: AH02454: FCGI: attempt to connect to Unix domain socket /run/php/php7.3-fpm.sock (*) failed
Update: service --status-all shows, that php7.2-fpm was also running. Maybe this was the troublemaker?
Unfortunately disabling php7.2-fpm and reinstalling php7.3-fpm didnt help ... ?