Installing parallels tools hangs after each update

Hi,

every time for the past few updates, parallels tools installation automatically starts, but then hangs at about 62%. When this has happened after previous updates, I've had to restore from a snapshot to get it to install. This time that doesn't work either.

I've read and tried this and this:
http://kb.parallels.com/en/117753
http://kb.parallels.com/112609

But they do me no good, because I need admin privileges, which I don't have, as it's a work account. Getting IT at work to help me usually takes weeks, and macs aren't officially supported.
I'm running 11.0.2 on a retina MBP running El Capitan, but this issue was occurring with Yosemite too.

Any further suggestions?
And more to the point, why does this keep happening?

 

Anyone?