I have a two week old Brompton that developed a chain issue in the past week. I have some idea of where the problem originated - I was trying to fold it recently and realized I had to move one of the pedals to get it to fold correctly, so I backpedaled it which caused the chain to come off slightly in the derailleur area. I tried my best to put it back on (which is tricky with how small everything is) and all seemed fine until yesterday when I noticed a clicking noise that almost sounded like something was hitting something else, which was only happening in 1st gear. At first it was just an annoying noise but then it started sticking and jumping gears. Then I started noticing it jumping gears no matter what gear I was in. It was also inconsistent. It would ride fine for 10 minutes and then the problem would be back, etc. Or it would be fine in one gear and a problem in another, but then would be a problem in the one that wasn't a problem and so on.

I've researched this a little and saw that some were suggesting tightening the IGH cable. I don't know if that's the same technique that is indicated in this Brompton YouTube video about adjusting gears - - but I couldn't understand from the video what they were asking me to do. What extends 1 mm? And how do I extend whatever I need to extend? What's the rod and what's the axel they speak of? Very confusing. I'm not super technical with bikes just yet and definitely not with Bromptons so it's frustrating that the video assumes what they're talking about will be understood and they don't show it very well despite it being a video.

I'm hoping someone can give some insight. I will take it to the dealer if necessary but they're across town and my bike is my transport so hoping I can avoid that especially since they'll likely need to keep it for a day.