Tilde shortcut duplicates my key When writing, I often need to use tildes like ó (but still need my keyboard to be in English), so I just hold the key down and press 4:



Usually it works fine. But several times have I ended up with this:



I don't know. It's like some sort of lag happens and the keystroke is repeated or something.

This is not software specific: it has happened to me in all sorts of applications with textfields. Even web browsers.

Is this a known problem? Is there a solution?

I am using Mac OSX Yosemite 10.10.3. I have a Macbook Pro 15" Retina Display Mid 2014. I don't use other Macs so I can't say I can reproduce this issue in them. I use the builtin keyboard.
I didn’t know that holding a key in OS X produced a list like that. Very useful!

Not a direct answer to your question, but may help you, is that if you type alt+e then o you will end up the the “ó” character. 

The alt+e combination gives you the acute diacritic mark, then you just enter the letter you want to put under it. So alt+e then e works to get “é” too. 

You can also do alt+e then shift+o to get “Ó”.