I have not, yet, broken a CZ spring, trigger return or other. I did, awhile back, replace some springs with reduced power versions.
I've read of broken trigger return springs on other forums. One guy said he bought a new P09 9MM and fell in love with it. Felt good in his hand, shot fantastic groups (he's a Glock guy and so he was really happy with the P09 groups) but something broke on it a few weeks after he got it. I don't remember what broke. he shipped it to CZ USA, they fixed it and returned it. Two weeks after he got it back the trigger return spring broke at the range.
He sent it back to CZ USA again, got it fixed and when they returned it to him he sold it. He said two breakage issues in the first month or so of use was too much for him to trust the gun for serious use.
I hear about lousy triggers. My P07 came out of the box around 3&1/4 to 3&1/2 lb. SA and about 8&1/2 DA. I thought it had a pretty decent trigger. Way better than the Glock/XDM/M&P pistols that preceded my very first CZ. The next CZ, a P09, came out of the box with a 1/4 lb. more effort required SA and DA than the P07. A little more "creep" before the hammer release, but the pull weight was pretty darned good.
Good and bad. Like cars, trucks, washers, dryers, refrigerators, etc., etc., etc. Some days you eat the bear, some days the bear eats you (remember Gardens of Stone?)