I’ve had it happen where mempool fees just happened to spike as the transaction was being broadcast… and it took a couple days to actually get confirmed. Just unlucky bad timing. I’ve always just waited it out.

This is the scenario where you could try replace-by-fee but it’s not something I can talk about from experience. You’d have to read up on it to see if that’s something you want to do. Sparrow is capable of it. I believe it will require you have more (equal amount) of funds available to replace the transaction currently in mempool.