I heard of a Maramu that had broken bolts.
The engineer that repaired it advised me to check the bolts....I did, and found they were a little loose.
I tightened them and now check them every month or so...and so far they are still tight.
I believe the problem is that they vibrate loose and after some hours of being driven in the loose state they break.
Also the way Amel assembled that coupling they are almost impossible to get out.
There are other older posts on the forum about this....and how to replace them.