If you have an alternating orange and white power LED, it means that the Deck is struggling to charge at at least the rate that it would on the official chargers (40W or 45W).
This could be you using an alternate (and lower power than the official) power adapter, or it could have been an electrical issue where you were plugged in, and there was some issue with the current you were drawing. Or maybe the power adapter you're using is on its last legs and isn't acting correctly consistently.
For your future reference, here's an old Reddit thread I found back when I got my OLED Steam Deck; I bookmarked it to keep the light codes handy.