ID 371415 - Running more than one session with GPU based nodes causes "Couldn't find Function ******** " to occur within Viewer and Frame Server

Problem summary
Users have discovered an issue with their GPU based nodes ( e.g ZDefocus & OFlow ), when having multiple applications open at once.

Users have reported this being reproducible in the Viewer:
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Unfortunately, the Support team have not been able to reproduce the issue in the Viewer, but we have seen the same behaviour within a Frame Server Render:
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Customer reported version
nuke.10.5v1

Customer reported platform
centos6​​

Steps to reproduce

1) Open Nuke

2) Set up a Node graph like the second image above  ( Ramp & Checkerboard into ShuffleCopy, then Downstream a ZDefocus node and a b node)

3) Open another Nuke application and copy the first app's Nodes.

4) Within both applications, modify the ZDefocus values   ( This may or may not display the Viewer Exception displayed above) .

5)  Within the First Nuke session, Render the Write node with the Frame Server to multiple frames

6)  While it is rendering, edit the second Nuke session's ZDefocus nodes

Result:  Multiple frames may fail due to the Render Error Exception described above.

Workaround
Do not run two Nuke sessions with GPU dependencies at once.

Reproduced by support

This bug has been reproduced in:
Nuke11.2v4 - Windows 7 - Mac10.13 - CentOS6.9
Nuke11.2v1 - Windows 7
Nuke11.1v4 - Windows 7
Nuke11.1v1 - Windows 7
Nuke11.0v4 - Windows 7
Nuke11.0v1 - Windows 7 - Mac10.13 - CentOS6.9 



Unable to reproduce bug in:
Nuke10.5v7 - CentOS6.9 ( User has confirmed the Viewer error occurs for them within Nuke10.5v1

Earliest version tested
- This issue appears to be in all versions of the product

Expected behaviour
There should be no errors within the Viewer or Frame Server.

Actual behaviour
Exceptions occur when more than one Nuke session is open with GPU based nodes.