Charlie Brown broke the deadlock for Forres after 61 minutes but Vale hit back with three goals in the last 12 minutes. Mark Smith levelled after 79 minutes and Connor Rennie put Vale in front after 82 minutes. With two minutes remaining, a Mike McKenzie penalty secured victory.
Elsewhere, a three-way tie emerged at the top of the table between Keith, Buckie Thistle and Turriff, with Turriff edging out Huntly 4-3 in a thriller. Keith won 3-2 at Formartine and champions Buckie held off Rothes 2-1 at Victoria Park.
Cove's early season form continues to elude them as they suffered 4-1 defeat at Wick, while Inverurie Locos won 2-1 at Fraserburgh. Brora Rangers were held to a scoreless draw at Strathspey, and it was a similar story between Clach and Nairn.