The library is the same as you are using, which is weird. I did have another one loaded too but removed it and rebooted the computer. Still getting the errors, so moved on to fitting a DIL relay I bought in a batch of five and received today. Well it seems I am in pillock mode again, the relays are 24V! Add that to ordering the wrong SOIC-16 adapters and things have not gone well!
I then started musing about how I could isolate the TxRx lines and had a chat with some fellow radio amateurs. One of the suggestions was a tristate buffer like the 74HCT125. Well I looked in my stocks but could only find an HCT126, which was a bummer until I looked at the datasheet. It is perfect for the job, all the logic levels are fine as they are. Quick lashup and it all seems to work as expected. I also remounted the DIL adapter as I need to lose some height for a smaller enclosure...
