Pull the grip off, the spring and detent pin should fall out. Take a look at the pin, it should be pointed on one end and flat on the other, someone may have placed a smaller detent pin in the wrong hole. next pull the safety lever out and inspect it, IMO it would be pretty hard to break a safety lever. Look down in the trigger assembly, there could be trash between the disconnector and trigger.
The hammer must be cocked to get the safety back in.