Thought this was in the wishlist topic at first and was prepared to vehemently oppose the request! Phew…
Anyway - I’ve sent duplicate trade offers with some regularity on mobile. I think I realized this happens because I tap the confirm button on the trade review modal multiple times. If the proposal date is the same for your trades, this may be what is happening to you.
I have had similar issues with multiple trades. I can’t pinpoint whether or not I’m returning to trade wizard, but definitely occurs when I’ve made trades using my phone.