After Effects - Errors on render farm

Hello,
I have some issues with slaves rendering after effects jobs. And maybe some clues for a very weird after effects error.
I’m using Deadline v7.0.2.3 R.

2015-06-08 14:35:47: 0: STDOUT: : Unable to receive at line 314 2015-06-08 14:35:47: 0: STDOUT: aerender ERROR: After Effects can not render for aerender. Another instance of aerender, or another script, may be running; or, AE may be waiting for response from a modal dialog, or for a render to complete. Try running aerender without the -reuse flag to invoke a separate instance of After Effects

the symptoms are the same as described at the en of the support guide :
http://docs.thinkboxsoftware.com/products/deadline/5.2/User%20Manual/manual/aftereffects.html

It occurs only on renderfarm machines, and not on workstations.
So I tried to increase memory usage in after effects job’s settings without any success.

We don’t have any special plugins, anyway the job render perfectly on a workstation.

Concurrent tasks was set to zero, so nothing is bad here.
I tried to increase it to 10, to see if something changed.
Some tasks started and some didn’t. From 10, only two started. The others returned the same error.

I tried to activate after effects multiprocess rendering option. And finally a jojb started and completed.
Everything is partially fixed, some tasks still crash at 50%.

Do you have any tips to solve this issue?
Thanks for your guidance.

Hello,

Can you verify whether there is already an aerender process running on the slave when the task is dequeued? It seems pretty clear but based on what you shared.