The left shifter and front derailleur work fine. The right shifter works fine if I shift to a smaller gear; the bike does not respond if I shift to a bigger gear. I plugged into my PC and from there I could shift with the rear derailleur; so I assume that is not an issue. I have had the bike about a year and it never had an issue until now (so, not a connection loose from assembly anyway). I have not unplugged/replugged any of the connections yet as I understand I would need a special tool for that. I would guess that if the shifter connection were the problem, then the bike would not shift either up or down. Anyone seen this? I hope I don't have to replace the shifter. (R8050 system, gravel road bike w hydraulic disc brakes) Thanks

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    Sounds like the Down button in your right shifter is either not registering a press, or not sending that signal. Given its already broken, I'd suggest you start looking closely at it with a multimeter and see what you can discern. Removing the shifter from the bars might be easiest – Criggie Aug 21 '20 at 22:28
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    There's like 4 or 5 strands in there so I wouldn't rule out it being a problem with the connection. By far the most common acquired problem I see with di2 is hand force gradually reefing on the connection and causing connectivity problems. The special tool is nice but you can improvise it as long as you understand the goal is be super gentle with the plug. – Nathan Knutson Aug 22 '20 at 1:51
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    Take the bike to the LBS where you bought it if it's less than a year old (two in the EU) Shimano has a fine replacement policy. I got an entirely new lever when mine stopped working. – Carel Aug 22 '20 at 7:07
  • Thanks guys! I bought it used (in USA) and it is for sure more than 1 year old now. Sounds like I'll start with shifter removal and checking connectivity. @Carel I'm sure yours was free but any idea what a new lever costs? I could only find the whole assembly in pairs (L/R) - therefore not too cheap! Thanks all – jhr Aug 25 '20 at 0:50

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