Classifying stems by metal vs rubber is an oversimplifying error -- It's not the material we care about, it's the pressure rating. Trailer tires using automotive stems are operating near the top end of the rating.
When one of my stems failed on the Interstate in Virginia, the nearest tire dealer was one that dealt mostly with big semis. They thought it quite cute when we pulled the Trillium
The guy told me that he would not never advise putting a rubber (passenger car) stem in a trailer tire due to the pressure difference. For a couple of bucks, we had all our stems swapped out to metal and have had no problems since.
Of course ANY opportunity like this should be taken to remind folks who use trailer tires
to be CERTAIN that the pressure is kept to the mfgs. specs. Low pressure results in increased heat and sidewall failure. We run fifty (50) pounds in our Carlisles, not 35 like the Dakota TV.