My experience with Weatherby service had been positive. I had a SA 08 12 ga that developed a problem with one of the pistons - a piece chipped off the o-ring. Called the 1-800 service number, explained the problem, supplied the serial #, etc - they said no problem we'll just send you a new piston - that is until they realized I was in Canada. I'd have to deal with the warranty centre up here, the nearest being Ellwood Epps. Ok, I contacted them via e-mail. They responded within a couple of days asking for more details etc. I sent the requested info along with pics and added that the US centre was going to just send me the part. Got a package couple of weeks later with the new piston - didn't even have to take the gun in. That's good service in my books.
Now the flip side. Decided to trade the gun in (2018). Went to two different LGS - both refused to even look at it citing the problems you mentioned. Both said they stand behind the products they sell and wouldn't take a chance on the semi (one said their pump was a great gun and wouldn't hesitate to take that). Eventually did find a store that would take it but it had me worried if I ended up keeping it.
Quite possible that the LGS service problems are more typical than what I experienced (a good anomaly ?) but you'll have to decide for yourself.