Something definitely wrong there then ....
As I said each to there own....
I don't think I've ever been on a boat with a sea toilet that did not have that sulphur smell in the heads to some degree.
Still maybe I have a sensitive nose.
As Refueller says the problem is down to users, one of the issues is in not pumping enough to clear the pipes and often require a large number of strokes. As for blocking with paper the crew need to understand how to use it and how much to use and most people don't seem to have any such problems. The exploding problem was no doubt caused by over pressurising and trying to force the blockage through again what one could describe as user error or lack of understanding. There is also the problem of a sulphurous smell after standing for some time that can be cured or overcome simply by flushing the toilet and pipes with fresh water and then closing the outlet valve. There is a world of information about the use and maintenance of sea toilets of all types for those prepared to look for it.
A case of needs must then and a problem of the Baltic, for me however it would just be a reason not to have the boat, I gave up camping and wearing hair shirts many many years ago, I like my creature comforts.
The Americans (God bless them) do a conversion kit for porta pottiesfor overboard discharge.
As for leaving to brew for 4 weeks would probably have the advantage of self emptying.
Chemical toilets also smell, require management, and have the potential for misuse.
Nothing is perfect, but on balance it works for me.