When the game crashes, conjurer servitors "usually" return after the crash. However, recently they'll return, and 5 seconds later, leave as if their time is up. There's not much point in having them stay with you after the crash if they're just going to leave immediately, leaving you with 50 hours (or however long) remaining until you can conjure again. I don't recall this always happening. Seems like a bug

Any more info you've got would help.