Electronic & Hydraulic Shifting (Di2, Ui2, customisations)

Thanks - that sort of thing was my guess. Will maybe dismantle for the fun of it.
Annoying as can only justify replacing it with ultegra which doesn't look nearly as nice.

There's a guy in the UK that repairs front derailleurs and rear derailleurs. He can probably tell you whether or not it can be fixed.

His name is Pawel Niewiadomy (https://www.instagram.com/paweln83). I've had more luck contacting him on facebook though. He also posts in the 'Shimano Di2 Forum' group on facebook (not my group, but I am a moderator): https://www.facebook.com/groups/shimanodi2