Has anyone had any problems with the new TC G2
action, and if so, what was the fix?

I have one and have had no problems. Although I like the style of the original better. The G2 is so easy to work with and paricularly if you are teaching a young shooter with it.

FYI all TC receivers and barrels have a lifetime warranty as long as some double thumb gun wrecker hasn't messed with them

When closing the action on a 23" 45-70 bbl, it would not be possible to cock the weapon, unless you'd slam the action shut. At the time I thought the problem was with the locking piece being not up to spec, so it would not reach far enough into the frame to reach the safetylever. however, I now have two additional barrels (one brand new, one that has been on the shelf of my dealer for years), and they suffer the same problem. So now I think that the G2 frame I have may not be quite to spec.
Solution is simple, however: I just "touched" the locking piece of each barrel with a Dremel tool, removing a minute amount of metal. The locking piece will then be a couple of .001" thinner, and thus will reach into the frame farther, so the safetylever will be pushed in.
This was easier than returning the frame to the factory, and had I screwed up the only loss would be ta tiny locking piece...which I got for free at my local gunshop anyway. (This guy still knows the meaning of the word service).

As far as the lock-up problem goes, I have a G2 and it does not work well with the single-piece locking lugs. I've had two barrels that I received with one-piece and changed them over to two-piece lugs and haven't any problems since. The third barrel came to me with a two-piece lug and it works great. TC gave me the replacement parts at no charge each time. The trigger on my G2 was heavy from the factory. I installed a Mike Bellm spring - #3, I think - and did the smoothing per his tutorial, and now have a crisp 2 pound trigger. The triggers on the older frames seem better to me, but overall, I like my G2 alot.

I have a G2 and I'm not crazy about it. The trigger was much stiffer than the Contender triggers, and I had to have a trigger job done. The rimfire firing pin flew off and is lying around somewhere at the range. I had to send an older .30 Herrett barrel to TC to get it to fit the G2 frame. And nobody that I know of makes a decent soft rubber grip for it, although Pachmayr has been saying they would have one this summer.

No problems with mine.

I got mine and had the lock up problem on several barrels that had the split locking lugs.
I called T/C and after a little "discussion" they sent me the newest style of locking lugs.
The new 12" barrels have a minor change on them that is different than the older style split lugs.
These did come at no charge when I advised them their new ads say the G2 works with ALL prior barrels!
I sill need to put in a lighter trigger spring and stone the action.
I love the easy open feature and the ability to recock it.