They fell behind in the 11th minute when Callum Wiltshire was on target, before Matt Loaring found the net and in doing so became GFC’s joint second top scorer of all time with 92 goals.
Anuar Ceesay put Badshot back in front, before Charlton Gauvain had an effort ruled out for offside before the break.
The Green Lions were down to 10 men on 61 minutes when Tom Dodds saw red after a crunching tackle and just eight minutes later they were punished on the scoresheet.
Kareem Akinibbi scored.
Gauvain then dragged Guernsey back into things again when he leapt on some lose passes, but the momentum only lasted a minute when the hosts scored again through Akinibbi for a 4-2 win.
One place above them in the table, Northwood lost 2-1 at home to Leatherhead, while below them both Corinthian-Casuals and Binfield also failed to pick up any points.
The Green Lions are at home to Thatcham Town on Saturday.