Random "servo lag" alarms on the older DC-drive Mazaks are indicative of a servo drive slowly going bad, or the power supply for the servo drives going bad.
You can slow down your max rapids, that can help buy you time.
The TRA-31 and TRA-41 drives, and the servo-drives power supplies (I forget the designation) are common on Ebay, purchasing one that was removed from a working machine is usually a good gamble.
Good luck with it...
ToolCat