This is extremely weird. My Fadal (4020HT with 88HS control '94 model) seems to have a corrupt fixture offset.
I can't run circular interpolation anymore on G57, I get an error "must apply fixture offset G1, G0 at Nxx".
As long as I don't have any I, J or Ks in my file it will run; otherwise I get the error.
If I take the EXACT same program and edit the G57 to Gxx (any other fixture offset I want) it will run perfectly. When I edit the program back to G57: I get the error again. Hence the conclusion that something directly related to that offset is corrupt inside the MCS. I have been toying with this for a week now.
Anyone ever run across anything like this?
Sure was frusturating for awhile.
Now just an inconveniance, I guess.

Never heard of this problem. Does the same thing happen if you use E words rather than G5x to define your fixture offsets?

I am not familiar with E words.
I quick explanation on how they are used instead of G5x?

The native Fadal description for fixture offsets is E1, E2, E3, etc....., up to E48 instead of G54, G55, etc.. . You use them just like you would using G codes. Fadal controllers are Fanuc compatible so you can share programs between both controllers. That is why you are allowed to use G5x to define fixture offsets. If you are having problems with G57 try using E7 and see if that works. Good luck.