ID 138224 - Swapping buffer inputs with Enter is very slow and restarts buffer caching/processing even with Pause button enabled

Problem summary
Swapping buffer inputs with Enter is very slow and restarts buffer caching/processing even with Pause button enabled

Customer reported version
nuke.13.1v3

Customer reported platform

Steps to reproduce

1) Open Nuke Studio

2) Import two clips (ideally two 4K Quicktime files from the network like \\netldn\netshare\support\4Pete\footage\Bambo.mp4 and \\netldn\netshare\support\4Pete\footage\Site_2_PondTrees.MP4) and add them to two tracks on the timeline above each other

3) Select the bottom clip and press 1 to load it into A buffer
 
4) Select the top clip and press 2 to load it into B buffer
 
5) Select the Viewer and press Enter to swap buffers. The Viewer takes a while to update and the caching/processing restarts.

6) Pause the Viewer updates, by pressing P.

7) Select the Viewer and press Enter to swap buffers. The caching/processing still restarts even though the Viewer is paused.

Expected behaviour
For the buffers to swap quickly without caching

Actual behaviour
It can be very slow to swap A/B buffers, and pausing the viewer doesn't help to stop it caching

Workaround
Unknown.

Reproduced by support
This bug has been reproduced in:
Nuke Studio 13.1v3 - Windows 10, CentOS 7, macOS 11

Nuke Studio 12.0v1 - Windows 10

Reproduced by QA in:
Nuke Studio 9.0v1 - RedHat6.3
 

Earliest version tested
Nuke Studio 9.0v1 - This issue appears to be in all versions of the product