Fixing the error "file lock acquire failed"
Often this error can be resolved in the following manner.
To test this, select one pair of servers with a common job for a trial.
With a plain text editor edit /FileReplicationPro/etc/s2s.properties file
find the item s2s.file.avail.for.copy.strategy=Lock
Change it to the following s2s.file.avail.for.copy.strategy=UpdateTimeStamp
Save and repeat on the other server.
Restart the job and observe.
If that does not work, reverse the changes on both servers to false and restart the jobs.