Lot of input from a new member. I would like to see the answer to Barliman's question about contacting Phaeton. The situation feels strange, even fishy. As Flugelgirl says, you get your local tech (or yourself) to change out valve stems.

Here is the next installment of Brass for Dummies, or Brass for Parents.
http://www.jaegerbrass.com/Blo/Entries/2020/1/explaining-brass-instruments---3-more-notes.html

A trumpet needs some resistance. One with zero resistance would be like that playground trick when someone leans on you but you pull away.

Here is chapter 2.
http://www.jaegerbrass.com/Blo/Entries/2019/12/explaining-brass-instruments---2-the-notes.html

@Vulgano-Brother You are jumping the gun somewhat. Shapes of curves will be addressed in a future Waiata.

@Dirk020 If one model actually had more resistance it just means that it was harder to get it into resonance. I am not trying to explain design principles. I am only hoping to point out information.

I put this one up to help clear confusion.

http://www.jaegerbrass.com/Blo/Entries/2019/12/brass-instruments-are-not-pneumatic-circuits.html

@tptguy One of Conn's preferred threads was 6-40

I have often been surprised at the lack of students' understanding of how trumpets work, so am fated to write some brief articles to help them. Here is the first effort:
http://www.jaegerbrass.com/Blo/Entries/2019/12/explaining-brass-instruments---1-the-basics.html

Especially where you are, I would check out Cerveny.