I have had a .54 cal. GPR flintlock for years & have shot Thousands of shots thru it & it has never failed me, never been a problem & it is still on the original frizzen. In fact, the only thing I have changed on this rifle is flints when they wear out.
Lets keep in mind this is a $ 300 rifle & the Lock in it is not the quality you may get from a company that builds locks & sells them. However, for a $300. rifle I don't think ya can beat it & IMHO it is the best buy for the money on a low priced RB rifle in percussion or flintlick.
As for putting a L&R replacement on it, no, I wouldn't. First because L&R makes it & second because you probably won't need it so why put another 1/3 of the cost of the rifle in it. It is a $300 rifle, accept it for what it is, learn to make it work & have fun with it. There are thousands of them out there being shot & the locks are working fine. No, the lock is not as smooth & fast as a Deluxe Chambers Siler, no the trigger is not as smooth as a Davis double set trigger, but again, it is what it is, a low priced mass produced ML. :-)
Oh, and I would brown it also.