The Rocks slipped to tenth spot in the Ryman premier division after suffering their fourth defeat in five games with a 2-0 reverse at Bury Town.
They conceded twice in the opening half-hour and could find no way back against their Suffolk hosts.
They now look to regroup ahead of Tuesdday night’s home Sussex Senior Cup quarter-final against Eastbourne Borough.
In the county league, the only local winners were Selsey, who beat Hassocks 3-2 at the High Street Ground thanks to an 89th-minute own goal.
Connor Cody and Jack Williamson were the other scorers as Adam Hinshelwood’s team moved up to 15th.
Pagham’s recent mini-slump continued with a 2-0 defeat at Sidley, who scored a goal midway through each half, while Chichester City lost 3-2 at Hailsham.
Midhurst’s fine form in division came to a halt in a 1-0 loss at Westfield.
In divisiion three, Sidlesham showed why they are top dogs with a 6-1 rout of Roffey - Dean Platt, John Phillips (2), Andy Hounsome, Billy Chatfield and Paul Barnes found the net.
Second-placed Barnham went one better with a 7-0 success at TD Shipley. Aaron Hancock (2), Mark Pedrick (4) and Joss Parsons were their scorers. Barnham are level on points with the leaders but have played three more games.
West Sussex League action included a 6-1 premier-division win over Holbrook.
Get all the local football action in the Observer - out on Thursday.