$1911

I think, its can be two problems:
1 weakly knots
2 it's too wide for one fastener

If yours bralets wider than 18 - 24 strings, you should make two fastener.
If you made weakly knots, often you can't saw it when you in procces. If yours braslets have less tnan 16 strings but but they roll up, your priblem in knots. So, idea about starch not bad, if you haven't darkly colours. If you have its, you can try do it with gelatine

As I suppose only beaded bracelet can have curl when you wore..As it has small beads which messed up with each other..Ironing work only if the bracelet is made of cloth or any fabric..

Starch tends to yellow thread over time. Also, it won't really work if a person wears their bracelet in the shower, or gets it wet. That would wash the starch out, and it would have to be re-done.

If it is a really large bracelet, have you tried backing it with something, like a fabric?