Re: Broke the bottom E string
Another possibility is a too-narrow nut slot for that string, which would mean that the string wouldn't "pull through" smoothly when tightened, causing too-high tension on that part of the string between the tuning peg and the nut. The kink where the string goes into the tuner hole, is a weak point, and excessive tension in the small part of the string between peg and nut, will often show up as a break at the tuning peg.
As well as checking the tuning peg for a burr or unusually sharp edge, consider rubbing the end of a #2 lead pencil in the nut slot for that string, to give a bit of graphite lubrication.
I agree about leaving enough slack in the string when putting it on, so that the string winds around the tuning peg several times when being tightened to pitch. May distribute the strain a bit more. Good luck!
Gibsn: '54 F5 3pt F2 A-N Custm K1 m'cello
Natl Triolian Dobro mando
Victoria b-back Merrill alumnm b-back
Stradolin Vega banjolin
Sobell'dola Washburn b-back'dola
Eastmn: 615'dola 805 m'cello
Flatiron 3K OM