Dampers on these guns are prone to corrosion which in turn can cause them to leak.

I have had cause to "right off" a 250 only a couple of weeks ago due to the damper unit breaking up causing the gun to recoil, this in turn created some internal play.
The knock on effect was the rearmost body tube pin split the body tube arond the location hole on the cocking lever side, the final nail was the cocking lever broke due to all the added strain.