Apparently the English youth players get impressed by the Jamaican reputation. So they end up switching nationality because of reputation. IF they do it because of play time, then that is one thing, but England should have better reputation. Any way to change it as it's really annoying?

yes you can change it

but as you can see that isnt the issue if you are etting lots of this sounds like a bug in game which you shoulf report to SI

 

for a current save change the players nationality and/or remove any second nationality etc