The same old chestnut keeps cropping up, namely oil from the hose.
It is NOT the hose which causes the problem, there is far too much oliy residue in most cases and if it were the hose, it would be shrivelled like a prune and so hard it would break as soon as you touched it, but they are not, they are still flexible and in generally good condition.
Even completly stainless steel installations suffer the same blocking.
The problem lies in the GAS, or rather the oil in the gas.
Why didnt the cylinder mounted regs suffer, because they are single stage regulators with one diaphragm and the oily residue passes through, into the pipework and some is burnt off, some remains in the pipes and eventually blocks the pipework, and can cause quite a lot of damage to gas valves.
GOK (Truma) regulators are two stage regulators, having two diaphragms and it is this setup which is allowing the oily residue to condense on one of the diaphragms and block the unit.
As a regulator it is very good at its job but because of the contamination in the cylinders it suffers from the problems we all know about.
If you want to have a go at anyone, have a go at Calor etc and get them to clean up the gas.
As it is at the present time, cylinders are only cleaned out every 10 years, soon to increase to 15 years, so the problems are likely to be around for a long time.
The only alternative to refitting a GOK regulator is to fit a Clesse single stage bulkhead regulator, but that will not stop the oily residue, you just wont see it until some years down the road.
PS It is not the caravan manufacturers fault either, nor the orientation of the regulator.