Feed per rev at 10% of programmed speed

I’m having a wtf moment. I have a known good program that ran before. It’s on a lathe, Program runs fine until it hits a G83 cycle , instead of feeding at .015 a rev, programmed in G95, it feeds about a tenth of that. Code afterwards won’t feed at programmed rate either. Canned cycle will run in G94 and ipm, won’t run in feed per rev, the rest of the program won’t run at the programmed rate either after the canned cycle. Program is returned to G18 . Ive programmed lathes for 25 years... what is going on with this? 

I’d say yes, since it cuts threads fine and everything in the program , ruff and finish turning ,work fine until it hits the line with G83. This is a proven program. Something here is wonky. This machine has worked with relatively few problems since 2014. It still has 2.6 on it and was upgraded to whatever the last incarnation was. I have had issues with using the canned cycles on a lathe before. Maybe it’s time for a lathe only version. There is a reason Fanuc, Siemens, Mitsubishi ect have specific packages.

Bad encoder channel on 7i77. Switched to a different channel. Original channel didn’t show a and b signals changing or raw counts. I have no idea why it was intermittent.