[MikeAurelius]

additional thoughts:

Regulators are notorious for not being accurate on the bottom side, especially the less expensive regulators which "some" companies sell to lampworkers. Even though the guage shows a maximum of 30 PSI, less expensive regulators won't be accurate until about 1/3 of the full pressure setting, in this case about 10 PSI, and as you noted, the fluctuation does seem to start to go away.

This is usually caused by not enough spring tension against the diaphragm - less expensive regulators use inexpensive spring assemblies and lower cost diaphragm materials.

I had a discussion with the marketing manager of one of the "other" suppliers - he indicated to me that they get a lot of returned regulators, then admitted that they buy the cheapest ones they can find.

My company sells the Smith brand. They are made here in the US, and are not the most expensive, but are up there in price, averaging around $95.00 each. In the 5 years we've been selling these regulators, I've had a grand total of 2 returned as defective, and when returned to the factory, it was determined that they were the result of the user not backing off the "T" handle at the end of every torch session, which put stress on the diaphragm.

I'm not saying this is what you are doing, but indicating that at least in the case of the regulators that I sell, this is the most prevelant reason for regulator failure.