Weight in the boat. I've sailed a fully loaded DS (one with a tabernacle) in winds that might have approached what you had. With none to light weight crew plus full set of expedition gear, supplies and water for a week. We had mostly downwind conditions, but one day we sailed close hauled, on the same tack, for a few hours. I'm thinking we hadn't reefed, because I remember I had to really work to keep her upright in the gusts despite all the ballast. Other than that, the boat felt more like a keelboat than a dinghy, but in a good, steady way.
The main difference is that we didn't have the waves to fight against (when we had waves, we were surfing them on the downwind parts).
I'm sure you had conditions that put more stress on your tabernacle than your other trips. And tabernacles are more sensitive to flexing/wave loads. That's the reason people advise against using them on moorings. But, with stainless steel screws, it's always possible you had stress corrosion or cracks.