I switched from classic 10s Ergo levers to the Veloce 10s Ultra-Shift levers this summer. As the temperature has dropped in the past week, I've started experiencing problems shifting the rear cassette (no issues with the front, though far fewer shifts there). The shift lever simply won't move all the way to the left--it jams, and no shift happens. After a few attempts, it will shift. Often, if I pull the lever back towards me, away from the brake lever, and shift at the same time, it works better--shifting either on the first or second attempt, compared to three or four without pulling the lever. I've searched for any info on this, and haven't found any. Is this a known issue, and I'm just not finding it online? Is there a better cold weather grease I could use in the mechanism?
I rode the previous levers for many winter seasons (down to single-digits, F), and I know they also had problems in the cold, but not this sudden. Around December or January, I'd suddenly lose the click sound/feel, though they would keep shifting, and if it was a long winter, the G springs would utterly fail before spring warmed up, and I'd have to rebuild. Sometimes, I'd make it into warm weather, and they'd keep running until fall (still with no click indexing, but shifting just fine). But they never had this particular problem.
It's possible the cold is coincidence, and something has started failing in the mechanism, and this is the symptom of that, but I've only been riding it 4 months, so roughly 20,000 shift actuations. That seems really early for a failure.
Does this sound like a normal failure mode? I have no experience with how Ultra-Shift acts when it breaks (it sounds like its a lot easier to fix--I hope that I won't be rebuilding them three times a year, rather than every 1.5 years, like I was used to).