So I'm a little geeky about TT bikes and parts. One part that has always had my interest are the SRAM R2C TT shifters but the approximately $300 MSRP seemed excessive for my budget. In doing some research it seemed some individuals had issues with the shifter going "limp". After reading it appeared to be a very fixable problem so when a pair of "broken" shifters went up on eBay, I decided to test my theory. Here are my "budget" SRAM R2C shifters.
The "broken" shifter
Loosen the screw in the red plate to separate the shifter from the body and expose the internals
Loosen the screw the rest of the way to free the silver plate covering the spring and remove the silver plate
You can see the spring is twisted and off center. This appears to be the main issue that causes the shifter to "break" and swing up and down without changing gears.
Center the spring back down around the black hole the screw goes through. In this picture you can see the metal plate where the beginning and end of the spring attach. The long center prong one the 3 prong side of it will go down in between the beginning and end of the spring.
Carefully put the silver plate down so as not to dislodge the spring off of the black screw hole. Then use the back end of a knife or similar to push the two black pieces on either side of the long prong. Finally, carefully reinsert and tighten the silver piece in with the screw and then re-attach it to the rest of the shifter mechanism. The shifter should not work like new.
This worked perfectly for me and allowed me to get some great shifters on a heavy discount. Be aware that if you shift it to the extreme (highest or lowest gear) without a cable attached, this seems to dislodge the spring and cause it to "break". I was able to replicate this easily and then "fix" the shifters again. Shifting back and forth in the middle range didn't create the same problem. Some individuals have mentioned that it has "broken" while riding and if you have significant friction in the cable routing (which isn't uncommon on some TT frames and aerobar combinations), then it can create momentary "slack" while riding. If this happens when shifting to the extreme, it could theoretically re-create the scenario that happens when you shift it without a cable thus causing it to "break". Admittedly, I haven't ridden these shifters much yet but I will update if something changes. So far they have performed perfectly and have actually exceeded my expectations as it replicates much of the feel of shifting normal SRAM road levers. I hope this was a help.