There's a block of wood in the laminate building up that area that's supported by a compression post. The compression post is supported by another block of wood in the bilge. both blocks are susceptible to water damage. The one at the bottom sits in the bilge and the one at the top has a hole drilled through to allow the mast wires to pass through into the cabin. Cracks at the base of the mast step are usually due to the bottom block failing. cracks on the top of the step indicate the block in the mast step is failing. It looks like this boat has both issues. I haven't seen a 25+ that hadn't had this issue before. They aren't too difficult to fix, but it does take some patients and time. I never got around to replacing the block in the mast step, but I did replace the block in the bilge. Here's a link to the project thread:
My wife and I recently purchased a 1980 Ericson 25+ and now it’s time for the work to start. The boat’s in decent shape for its age, but the main concern is the compression post base. The block supporting the hull liner directly under the compression post is rotten and needs to be replaced...
ericsonyachts.org
25+ are also susceptible to cabin top core delamination. The top skin of the laminate is pretty thick, so it doesn't feel spongey when the balsa turns to mush, but it should still be addressed. You can easily tell by looking behind the headliner zippers next to the companion way hatch. Since the bottom skin of the laminate is transparent, you can see the core. If it's black, you know water's been getting in and rotting the core. Here's a link to the most recent thread:
https://ericsonyachts.org/ie/conversations/re-coring.13347/#convMessage-17456
Both projects are doable and I would do it again if needed. The 25+ is a great boat! good luck with the inspection.