If you have replaced the bottle then I would suggest the regulator is the next item to be replaced in order of cost.
Not sure what regulator you have but there were some reported problems with the Truma regulators sometime ago, which I think showed up as poor flow/low pressure, so if yours is a Truma it may be worth changing
If no one comes along shortly with a better answer it may be worth doing a Google on "Truma Regulator poor flow" you will get a substancial number of hits which may help your decision.
also change you pig tail between your bottle and reg, the best thing is to change to a stainless one but there not cheap, if its to steep just get a new rubber one.,
I asume you are using Propane gas which works better in cold weather, if not do so.
I had 3 Truma bulk head fixed regulators, and in the end went for the Gaslow kit with a regulator/ stainless steel hose with hand tighting wheel, no more problems. Cost about £70 odd but well worth it.
It did not seem to matter to mine which went down the same way and try to get the oily liquid from the system before yoy fit the next one.
I did'nt and the mixture of liquid gas and deposits made for some exciting flames in the MH.
The connection to the fixed gas pipe with the ermeto fitting on has prompted me to keep a screwed hose connection in the van and any more bother and I am going back to the bottle fitted reg. and making the output the old tried and trusted way.
------------- She says She does sex and cooking and I do everything else