One test, but that goes against all the rules and if you get caught you get into a quilombo more or less, is to take out the meter and connect the regulator directly to the pipe, if this persists, something is wrong with the new regulator or the pipe, if that works, the problem is the meter and you will have to resort to the supplier to change it, you may be inspected by the installation. I think the best option is to call an enrollee and take charge.
LUCK