It’s also worth reading this wiki: 🇺🇸 Monzo in the USA [Wiki] as it mentions the apparent double-charge at the restaurant as a “quirk” of the way payments are taken in US. This could equally apply to the gas station as well.
Simply put the restaurant requests an authorization for the bill amount, and then later requests another auth for the total including a tip.
The original auth will never be presented so will “undo” itself after a few days.