Settling?
If you search through the archives here you should find quite a bit on the issue of settling of certain models of Ericsons. (search on u079721 at least, as I have commented several times.) It's mostly an issue with the 38s, but I think some 34s have seen it too.
Basically the weight of the keel pulling down on the cabin floor causes the floor to sag a bit, and the hull deforms slightly until it reaches a new equilibrium, and then it stops. It isn't really a structural issue, by which I mean that the boat isn't falling apart, or the hull isn't failing. It's just that the design of the hull and floor aren't quite adequate to keep the original design shape, and a bit of "settling" occurs with the boat in the water.
When we first saw our E38 it was on the hard. But when we launched we noticed that the floor had sunk a bit, and exposed an inch or so of cabinet along side the floor that had previously been covered up. Later in looking around I noticed the same failure of the tabbing at the edge of the cabinet that you mentioned.
About 1996 or so I called the factory and spoke with an engineer there. He said they were aware of the issue, and that the solution was to run a structural bar across the cabin sole athwartships to hold up the floor, or tie the floor into the cabin overhead with a pipe. Or do nothing, as it didn't seem to really be a performance or structural issue once the boat had reached a new shape or equilibrium in the water.
So I did nothing. We hauled the boat each fall, so I had opportunity to see the floor all the way up, and down when in the water each year. And while I think the settling did increase a bit over the years (1994 to 2004) that we had the boat, it still wasn't that bad. When we sold the boat I was expecting the surveyor to notice the issue and bring it up, but no one did.
So I wouldn't worry about it, but do keep an eye on the amount of separation and see whether it increases.