I also own a MH40-2013 and have had the main window leak problem. I removed them and resealed, them, so far so good.
Just before the purchase the PO had done an expensive repair on the SD50. I have since become aware of the SD50 issues, which seem to be the oil recommended harms the bronze bushes, and the leg also becoming pressurised. So I have changed the oil type, and fitted a breather, both easy fixes and the info I see online suggests that this will be successful.
I had problems with the anchor chain jamming in the hawse. The pvc tube hawse delivers the chain to under the front bunk, however does not flow well and bunches up after 20 or 30 metres of chain. My solution was to cut the pvc tube much shorter higher up so the chain drops down into the area between the front cabin bulkhead and the bow, plenty of space there. I also heated the pvc tube with a hot air gun and put a radius downwards in the tube so the chain raises cleanly and does not catch any sharp edges. Just as before some of the chain does flow down under the front bunk, but there is now no hawse to jam in.
I also had a major problem with the swim platform. The swim platform has a centre ss pipe running across side to side to accept the axle bushes. This ss pipe was not well installed and the attachments collapsed , the pipe and bushes were then free to move in the side panels of the swim platform, which became unusable....major problem. However removed swim platform, installed access ports each end, reglassed ss tube and fitted new bushes and axles, now good. I suggest you look hard at the swim platform mounting, however the issue is quite fixable now the solution is apparent.
Another anchor issue is that when deploying the anchor as it starts to leave it pivots and the shank knocks up into the genoa furler, similar when bringing back on board, so anchor needs attention and help both ways. I am about to fit a roller above the shank and just below the inside of the furler, so the anchor cannot bash the furler and will self deploy and raise.
All of the fixes I have done were not difficult, however brainstorming the fix was much more difficult than applying the fix
It is a nice comfortable boat, the dc/ac, plumbing, and lpg gas systems all well installed and work well.
Interested to hear how you go with your prospective purchase, happy to provide whatever other info you would like.