Since you're asking a second time and I can't find a NCAA football game I'm interested in I'll chime in with my un-expert opinion. The boat wasn't built that way. The bulkhead is structural as are most that span under the companionway. It doesn't need to be heavy plywood to stiffen the structure. My guess would be that bulkhead is tabbed to the hull but not the liner. It wouldn't be tabbed to the liner anyway as the liner is not structural in most boats. Nevertheless something has moved and it is good to understand why it moved. I can totally buy into the settling on the trailer theory. Trailer bunks or rollers do not support the hull the same way as H2O immersion does. But the boat design and build should stand up to that. Some other forces that could separate the hull bulkhead from the liner could be rig tension, a grounding, collapsing mast support, collision, beaching, dropping the boat, and probably some others.
What would I do? Probably nothing. I had a Mark 25 which was a bit on the flimsy side. It would oil can badly and made horrendous noises as the liner and hull worked against each other. And I sailed it in some pretty rough water. I sold it because the marina was charging me for 30' as a minimum and I thought I might as well have a 30' boat. Hence the Ranger 29. I miss that dis-functional Mark 25.