Running multiple instances on the headless server will cause the wrong RGB images

Hi, Matt @mattdeitke,

I am trying to run multiple AI2THOR instances on a headless server with multiple GPUs. I have correctly started x server and have passed the test on a single process. However, when I run multiple processes, the simulators will return the images that do not belong to themselves, as the process 2 simulator will return the process 1 simulator's image. But it will not happen on a server with a monitor. I wonder how I can fix this? Thanks!

BTW, I am using and have to use AI2THOR 3.1.0. And my system is ubuntu 20.04 with Nvidia A5000 GPUs. A similar issue has been mentioned in #1007

Thanks again!