My Capri one's a bit dodgy also, you have to press it and kinda giggle it around for the contact to get happy for the horn to work.
Defeats the purpose a bit, as by the time you get it to contact, the idiot has usually moved on.
I did find something out though last year when there was no horn at all. 20+ years ago when air horns were the rage,I sprung for a triple set, decent italian(?) jobbies. The last year, nothing, just a wheeze, like a cat hacking a furball.
Apparently you need to lube them up once in a while. A few drops of spindle oil down the compressor, bingo!.
The next dodgy deliveroo nearly backflipped off his moped, thinking he'd just cut off a Vline N Class.
But it was just a mild mannered, 1600 pastel blue Capri only driven on sundays.