Here is a perfect example from Prospect's match against Barrington. With rooks on the board, the ending was likely a draw even though White would be down a pawn, but the king and pawn ending with even material was lost for White.
After 33. Kf4 bxa5 34. Re8+ Kf7 35. Rb8 Rb3, Black is going to find it very difficult to capitalize on his extra pawn.
The problem for Black is how to get his rook out from in front his b-pawn without losing it once he gets the pawn close to queening as in Pos. 3.
If the White king were on f3, Black could play 1...Rf1+ followed by 2...b1=Q. If the White king were on f2, Black would have the tricky 1...Rh1! 2.Rxb2 Rh2+! winning the White rook. However, if the White king stays on g2 or h2, or in front of its pawns on g4 or h4, the Black rook can't move without losing the b-pawn. That means that the Black king will have to come over to help, which will give the White king a shot at the Black pawns.
Unfortunately, White played 33. Re3? After 33...Rxe3e+ 34. Kxe3 axb5 35 Kd4 Kf7 36. Kc5 Kf5 37. Kxb5 Kf5, White got his pawn back but his position was dead lost because he could not stop the Black king from getting at his remaining pawns and his king is too far away to get at the Black pawns.
Even if the Black pawn were a file closer on c5 as in Pos. 5, the position would still be lost for White.
Now the White king has time to capture the Black pawn and to get back to block the Black king from getting to the White pawns. 35 Kd4 Kf7 36. Kxc4 Kf5 37. Ke3.