Hi Roland,
Firstly the babystay. In my view, the way Marine Projects chose to attach babystays to the deck, in those Moody's that have a babystay, was poor engineering. Basically, a short stainless steel tube was moulded transversely to the underside of the deck. Before installation, this tube had a stainless steel plate fastened to it, welded if I remember correctly. which protrudes up through a slot cut in the deck to create the point for anchoring the stay. Over the years, the relatively high loads in the babystay cause cracking in the deck around the hard point and water starts to get in, wetting the balsa core and so weakening the deck. Remember, babystays were invented to save money by doing the job of two forward lower shrouds, so really need to be well secured.
The shrouds are well attached to their stainless steel chainplates which are bolted to marine ply (?5/8" or 3/4") part bulkheads which, in turn, are securely tabbed to the hull from deck height right down to below the saloon settee bases. the top end of the chainplates stick out through slots in the side decks so the shrouds can be secured to them. As Pete says, the slots through the decks are sealed by little stainless plates screwed to the deck with self tappers and sealed with some mastic underneath. The original mastic used had a tendency to dry out and crack, so letting deck water penetrate. If not attended to, the water would eventually saturate the marine ply of the part bulkhead and start rot. In extremecases, the bolts fixing the chainplate to the part bulkhead can tear through the rotten timber at which point the wider lower part of the chainplate tries to pass through the deck with messy consequences and a possible loss of the rig,
Access to the chainplates for serious work, requires removal of the beautiful teak shelving or cabinets (depending which model). For inspection, many members have cut ~3" dia. access holes in the boxes surrounding the chainplates and covered them with plastic vents, dinghy hatches or offcuts from teak decking jobs screwed in place. The more tech happy folk have bought an endoscope to make the inspection easier and more thorough, as outlined in this thread:
A good way to detect incipient problems in either the baby stay or shroud chainplates is to take a straight edge with you when you inspect the boat. If you detect any bulge in the deck immediately around the chainplates, more investigation is warranted.
In either case, repair is possible and has been done, both professional and diy. Guidance for repair is available to members on this site, but a professional job in either case will cost, largely becauseof the access problems consuming labour time.
Peter