I have 2 OPD tanks, a 2gal and a 5gal. The 5 I use on the bbq and the 2 on my boat heater, I've had no problems with either in over 1.5yrs of use. The only reason I can think of, as to your problem is that whoever is filling them isn't purging the air out before filling. I had the same problem on an earlier tank used for my crab cooker, the station didn't purge the tank before the first use, took it back had it purged, problem solved.
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