A low-pressure regulator that held 30 mbar all summer read 41 mbar on the first morning below freezing. The usual suspect is the diaphragm going stiff, but in this case the vent screen had a film of dust and old sealant. Cleaned the screen, left the unit at room temperature for an hour, and the reading settled back to 30–31 mbar under the same load.
Worth checking before ordering parts: creep that disappears once the body warms up is almost never the spring.
Tare weight stamped on the collar is the empty weight of the shell, valve included. If a nominally full 11 kg cylinder weighs less than tare plus 11 kg, the difference is not always theft or a short fill — a cylinder that has been standing for two seasons can lose a noticeable amount through a weeping valve stem.
Soapy water on the stem, not on the thread, is the fastest test. Bubbles the size of a pinhead are enough to empty a cylinder over a winter.
Upright, outdoors, shaded, off bare ground. A pallet works. The two mistakes I keep seeing are cylinders laid on their side "to save space" and cylinders kept in a sealed shed that heats up in the afternoon. The first lets liquid reach the valve; the second cycles the pressure every day.