There is also a new iLOK/PACE software update that fixes the PACE 5.1 blacklisting at random issue too.
This had been, er, bugging me for a while now & it seemed to happen sometimes but not all the time & it turned out to be a PACE bug. The software update (launch the iLOK manager and it should be offered) fixes this – and you don’t even need to restart after installing it either.
Yup! SoundToys 5.3.1 and Xils StiX had the blacklisting problem, too, and the 5.1.1 iLok update fixed it for me.