GPU dispatching of calls can be multithreaded without a reason to share GPU objects data such as render buffers. But you have 2 different contexts, you cannot batch them together as by picking what to share and what not.

Cacks said:
I didn't want to have to make new classes per queue

I recommend using object oriented design here. You need one new class, a locked queue, that is a queue. You can distribute the logic behind locking the queue all over your code, and get problems like you are experiencing because reasonin…