The only ones that have ever been released that I know of are submarine sinkings, which included lost missiles on the bottom of the ocean. Other than that — we don't know.

There is the possibility that of course they had them but didn't ever say anything about them. The fact that the US had so many, and the Soviets did have several submarine problems, implies that you would expect there to be a few others in different parts of their similarly vast nuclear complex.

But there is also the possibility that they may not have engaged in the kinds of risky activities that the Americans did that caused their Broken Arrows — almost all of the American Broken Arrow was a result of the US bomber force, and many were a result of the US practice of routinely flying planes with live nukes onboard. This is a very dangerous activity to do routinely; the chance of any one plane crashing or having a problem is low, but when you have nukes in the air 24 hours a day, for years, you will quickly hit the numerical odds of having a major problem. The Soviets were less bomber-dependent as the Americans, and that might make up the difference.

Anyway — the short answer is, "we don't really know, other than the subs."