I have a little pocket trumpet I bought a few years back. It's an inexpensive one that everyone warned me not to buy because the valves are known to have problems sticking. I bought it anyway.
🙂))
I'm never afraid of mechanical problems because I'm pretty handy with that sort of thing. The valves were sticky when I first got it, and it was impossible to play because of that. However, I just took the valve assembly apart and lapped the valves in periodically. I slid them in from both the top and from the bottom when lapping them. I didn't even use a lapping compound. I just used standard trumpet oil, and just kept working with them.
After I did this they would be free for a while, and then start to lock up again. So I'd just lap them some more. I kept doing that over a period of a few months with longer periods of "playability" before they would start sticking again each time. Finally they quit sticking altogether and now they never stick. It plays pretty slick now. So it was worth buying for me. It was only about $200 or $250 I don't recall exactly. But I was told that it's almost impossible to find a good pocket trumpet for under about $700.
This one is pretty slick now. The sticky valves seemed to be the only negative, and like I say, they don't stick anymore, they are very responsive and work freely, quickly, and smoothly.
This picture is just from the Internet, but mine looks identical to this one.
I don't play it a lot. I just don't like doing all that 'brrrrring" with my lips. That's a shame too because it's a cute little bugger.