HI,
I'm having the same problem.
Mac OS Sierra 10.12.6
I run a number of music applications but VEPro 7 is the only one that rescans the Plugins every time I boot it.
It also takes its time to stop the process when I hit Cancel or Skip.
I have a pretty good idea of what's under the hood and what processes I have running and I can't see what would be trashing the Cache forcing the ReScan.
This also happens if VE Pro is restarted in the same session without the computer having been restarted.
I'm not using Time Machine et al.