Frequency of repair, and cost of repair, aren’t the same thing.
Having ruined more than a dozen basic shooter class shotguns shooting clay sports over the last 25 years, I would say, a decent box lock with longer barrels like maybe a BSS, it’s about as good as you can do.
Myself, I have grown tired of sending guns off to be repaired.
Here in the United States, having a gun re-jointed is many times more expensive than it is in the UK, so, it’s a much bigger deal when your gun starts to get loose.
The browning side-by-side’s, truly are a great shotgun for the clay sports.
Or perhaps Ithaca SKB, if you like something a bit lighter. They're hard to find with 30" barrels, but they did make a Model 100 Magnum with factory recoil pad and 30" barrels. In both cases (Ithaca SKB or BSS), you'll pay a premium for the 30" barrels. Stick with 1 ounce loads at modest velocity (or even 7/8 oz for closer targets) and you can likely put a lot of shells through either without needing to have the gun rejointed.