5 minutes ago I realised that the soft-ish plastic rope ladder thing on my NEW pirate ship snapped at the top

5135-ship and front-mast, I assume?

With the 5135s we get the same problem as with the 4424 (US 5736) Blackbeard's ship: the riggings (mast-"ladders") are too tight on the front mast, in every set!

The riggings might be a few mm too short, or the mast a few mm too high. Problem can be solved by sawing off carefully 2 or 3 mm from the top of the mast.
(not too much, otherwise the riggings will sit too loose. But if one would saw off too much accidently, then again that can be solved by putting something very small & flat in the mast-hole in the deck, so then the mast would stick a bit out longer and thus the riggings would be tighter again).
To stay on-topic: I have a goat but it is one for the lowlands.