checking for leaks is always a good thing to do any time we open the line or do any major moves as it does happen and the leak can be very sneaky.
Part of the problem is that we get so used to looking at gauges and assuming they will let us know when the tank is going down. NOT TRUE for compressed gas gauges, as they do not read levels but pressure and will not show we are losing gas while the re is still liquid left to become gas and keep the pressure up!
so what folks may get into is looking at the gauge and seeing 800PSI or some number and not spot that it doesn't change, except for minor temperature effects, until we have lost nearly the whole tank of CO2. Then once we get down to all the liquid turned into gas, the pressure does start to move down progressively---but that's not until we've already lost most of the tank!
Sorry, you may already know that but I feel it's always worth mention!
Reason for me to mention now is that part about getting a reading when you do turn the pressure full up. If you had a blockage, the added pressure should not increase the reading but if there is a pretty big leak in the meter, a certain amount may be going out the leak and increased pressure may force the meter hand to move a bit.
Not saying that is the true picture, just more a headsup to check, just to avoid blowing through a tank needlessly? Just lots of small points to confuseus.