Cam and a half bows aren't immune to timing issues. Sure, they're more forgiving, but even twin/binary/dual cam bows are susceptible to timing issues.
BUT, you can check timing yourself with the help of a friend. Hoyt Cam & 1/2 cams have witness marks to help you determine if you're properly timed together, and of course, you can have a friend (or use a draw board) watch your draw stops as you draw the bow to confirm that they're making contact simultaneously.
Personally, I'm with you. I don't trust shops. Period. So few of these guys are actually skilled or knowledgeable, and you can (as you are now) end up running a rat race trying to find the help you need, all the while, at each shop, they're probably tuning something FURTHER OUT OF IDEAL thinking that they're fixing the problem.
There's a million different things that could be wrong, from fletching contact to improper arrow spine to cam lean etc etc.
I'd start at ground zero as if you had just bought a used bow, and put it through some troubleshooting and "standard bow set up" paces.
PM me if you want some help trouble shooting, I'm not a paid pro tech, but I play one on tv (or rather in my own shop, setting up, troubleshooting, and tuning about a dozen bows a year for my buddies). There are few things in life that I enjoy more than a "problem bow". So many things to tinker with, and it's oh so enjoyable when she finally starts stacking sticks!
