Nobody can deny it. Bootstrap is bloated. There's a good reason for that - it's the jack-of-all-trades, the swiss army knife, the (not so) little framework that could. If you want it to do something, then it probably can.
The downside of this is that sometimes you experience mysterious problems...
When we got reports from our QA testers of various form elements randomly missing a border, padding or margins I wasn't too fussed. Maybe a junior had committed bad code, or the caches on our servers were playing up.