ID 472462 - Nuke processes do not free RAM after completing a render, including with the frame server

Problem summary
Nuke frame server processes do not free RAM after completing a render.

Customer reported version
nuke.13.0v1

Customer reported platform
Windows 10

Steps to reproduce

Method 1:

1) In Nuke with default settings, create a Checkerboard and a Write node.

2) Add a file path to the Write node with any extension.

3) Render the file with enabling the frame server knob.

Method 2:

1) Create three Nuke scripts, with Read node pointing to different file in each script, and a Write node

2) Open Command Prompt/Terminal, and launch Nuke in terminal mode, with the -t flag

3) Open the first Nuke script by running the command: nuke.scriptOpen('path/to/nuke/script.nk')

4) Check the RAM usage

5) Render some frames from the Write node by running the command nuke.execute(nuke.toNode("Write1"), 1, 10)
6) Check the RAM usage again, it is now much higher

* More complex scripts and longer frame ranges make this worse

Expected behavior
The RAM should clear after rendering

Actual behavior
RAM is not cleared from the Nuke processes after rendering completes.

Workaround

Close and relaunch the Nuke process to flush the RAM.

Canceling the render kills the frame server process which frees the RAM used by the Nuke processes.

Reproduced by Support:
Nuke 13.0v1 - Windows 10, macOS 10.13.6, CentOS 7

Nuke 12.2v1 - Windows 10, macOS 10.13.6, CentOS 7

Nuke 12.1v1 - macOS 10.13.6

Nuke 12.0v1 - macOS 10.13.6

Nuke 11.3v1 - macOS 10.13.6

Nuke 11.2v1 - macOS 10.13.6

Nuke 11.1v1 - macOS 10.13.6

Nuke 11.0v1 - macOS 10.13.6

Unable to reproduce bug in:
Nuke 12.1v5 - Windows 10, CentOS 7

Nuke 10.5v8 - macOS 10.13.6

Earliest version tested
Nuke 12.1v5 - Windows 10, CentOS 7 - This issue doesn't appear in this version and has regressed

Nuke 10.5v8 - macOS 10.13.6 - This issue is on all versions with frame server available in macOS.