Another thought that crossed my mind as I was nodding off last night...dangerous I hear you cry.
On both occasions I fitted 'used' strings. Probably already having a weakened area at the bridge end.
So maybe would be quite a good idea to fit new but cheaper strings first.
cheers, Mark.
Yeah. Prestretched strings often don’t like being restretched. The thing to check would be where are they breaking. You will probably be able to work out why once you pinpoint where they break.