Strings breaking at ball end with Mastery vibrato

[thegumbootman]

I've had a Mastery vibrato for a few months and I've just had a high E string break at the ball end for the first time. I use Elixir Optiweb strings.

Is the problem more likely to be with the vibrato or could it just be a defective string? And is soldering the ends enough to fix the problem?

[TeenageShutdown!]

There could be a tiny metal burr at the hole chafing the string. This would require some gentle filing with a round file. It could be just a string issue too.