Backup error (Backblaze) - Unable to find scope in lookup table, this may be caused by attempting to transport call contexts between AppDomains (eg. with remoting calls)

After many hours of recovering from a failed update I’ve finally got Duplicati running again on headless Ubuntu, emptied my Backblaze bucket, set up a new backup task (the whole thing went out of sync and was irreparable) and on trying to start the backup I get this error:

Unable to find scope in lookup table, this may be caused by attempting to transport call contexts between AppDomains (eg. with remoting calls)

I found this discussion but when trying to install/reinstall Mono I get a ton of other errors. Before investigating that, can anyone confirm that this is Mono-related or could it be something else?

Thanks,