Waltham Forest are back in the Essex Senior League's bottom two after a 4-2 defeat at Barking which was shrouded in controversy.
The Stags made the ideal start when Jose Agua headed in Jamal Mahir's cross after 11 minutes.
But James Peagram equalised for the home side just before the half-hour mark.
Six minutes later Joel Barnett headed in from close range.
Forest were left incensed when Ellie Mbangu was sent off for retaliation despite being hit in the face by Barnett.
Peagram added his second from an offside position before Lamar Reynolds grabbed Barking's fourth, again from an offside position.
Miguel Lopes de Matos scored a late consolation for the visitors.
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