Since I rebuilt my server I have been seeing issues where my use of the transcode-video docker image would consistently fail to complete the encoding process with this error.
transcode-video: invalid byte sequence in US-ASCII
The linked post led me to the solution - I needed to update the Dockerfile for my version of the image to include additional commands to configure the locale. This was a pretty easy addition as I already was using my own to customise a couple of things. I do not know why the appeared, but all I really care about is that it is working again now.