Seen this before!
Oh yes, I have seen this many times before! During a critical update that had been delegated to someone in the 2nd line support team, they had updated the DNS Zone file and accidentally added a hash instead of semicolon. Cue the phone call to myself at silly o'clock advising they deployment is not working and they are not sure what the problem is.
Eventually, I awake and identify that there is a hash on the prior record that was wanting to be commented out, however, in this case, there were also hidden characters as it had been amended via windows so also had to run dos2unix on the file and then re-update the file. I don't miss being woken up at silly o clock for these type of things :D!