I see your getting some views but no replies.
Maybe a moderator could move your question over to the "Winnebago Owners forums"
JMHO: Could have been a one off problem, or some how owner caused. Multiple trips on bad roads, for example. Seized shock even. Without seeing the failure , hard to tell anything.
Towing , particularly 4 down puts no strain on the rear suspension that would contribute to a shock or mount failure.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.