Thanks for your time once again @Gary_Verhaegen, my colleague working on the architecture for this was able to use your answer from my previous question today to determine that this is caused by a certification validation error. This is only shown when using a logback configuration file where logging setting can be overidden.
For posterity/other users, Gary’s explanation on how to change the logging can be found here: Is it possible to change the log level for the JSON API jar?