Thanks for the response! Apologies for not giving more detail.
This is showing in the kern.log while running Orthanc in Docker as part of the osimis/orthanc:18.4.4 image:
We are currently still using the deprecated Osimis Web Viewer;
As part of the switch away from this we will be upgrading the underlying version of Orthanc, which I think is now about 3 years behind.
My first guess with the issue I described would be that upgrading the version of Orthanc might fix the issue. But, before resolving to that as the solution, I wanted to double check if anyone had any idea what might be causing this, so as to feed back this information.