Despite others disagreeing I'll stick with what I said and did not say it was the absolute reason but a possible cause. You can easily & cheaply replace the breech seal, it won't hurt anything. You can also easily shim the top half of the breech seal (light fishing line as an example) and see if either of these things help. Simply get a black marker and touch up where the blueing is worn and see if there is any wear issues after. Otherwise if you have not noticed power, accuracy or lockup issues you could always leave it alone but keep an eye on things...
