I had a similar problem after having gaslow fitted a couple of years ago. We were travelling to France on M1! and starter to smell gas and there was a hissing coming from the top of one of the tanks ( we had filled them both the night before). We were going via the tunnel, so would not have got anywhere near the train before being stopped. I made a frantic call to Gaslow and fortunately we were not that far from their HQ so we agreed to return to them so they could check the tanks. In the end they provided a temporary fix to enable us to go on our holiday and we agreed to revisit them on our return journey. Not quite sure what the problem was, but Gaslow replaced both tanks and thankfully we have not had any repeat of the problem. Can't praise Gaslow enough for the time they spent with us trying to get to the bottom of the problem and the very helpful approach. I hope you manage to resolve your problem.