Downgrading to 1.18.0 (thanks for the link) has worked for me - I think deleting the .atom folder helped a lot as previously I was only deleting the Pymaker package folder.
Thanks for the tip on Filezilla/Putty, I have used that approach before and was just about to go back to it!
I also tried to get VSCode working, it looks pretty similar to Atom but I had issues getting the Pymakr plugin commands to work - just kept saying they were missing. Would be nice to get a more complete IDE for development as I have a few ongoing projects with the boards and find it a bit tedious switching between them and sharing the common code base.
Thanks for everyone's help.