The first happened about two and a half years ago carrying a PT1911AR (RH - IWB). It was hot (August) and I was sweating pretty bad. The DH apparently absorbed so much perspiration that it lost shape and failed. While I was getting back into my Sequoia my weapon slipped out hitting the seat and door panel on its way to the ground. Not a happy day. I replaced it with a SuperTuck.
The second DH failure was under similar circumstance (hot, sweaty) but carrying my Glock 36. Same failure, only this time the weapon simply oozed out into the seat. Replaced it with a TX Tuck from Rockin bull Leatherworks and haven't had a problem since.
I'll never own
another Don Hume, but that's just me.