You may have just answered what I was about to ask... I've been on VEP 5 for ages because everything has just worked flawlessly for me, and I haven't had enough downtime to roll the dice. However, I just got a new main Mac running Mojave, which has necessitated some updates, including VEP. This throws a wrench into my whole setup since all machines need to be running the same version of VEP - and some of my slaves are older machines. Grrrrrr.
Anyway, I just installed VEP 6 and nothing's working right yet - so before going through all the troubleshooting, I thought about going right to 7 since I had to buy new licenses anyway. I'd rather do all of this just once, but if 7 isn't ready for prime time...