Sills and Betteridge Lincolnshire leaders Boston United Reserves had their lead cut back to just goal difference after going down to second placed Hykeham Town.
The Pilgrims were beaten by the odd goal in three at the Memorial Playing Field to end their unbeaten run of 11 games.
Lincoln United Reserves consolidated their fifth place with a tidy win at Gainsborough Town, while Skegness United climbed to sixth with three points at home to Heckington United.
Skegness Town hit Grimsby Borough Reserves for six at Blossom Way to sit four points behind the leaders in third.
Gainsborough Town 2 Lincoln United Reserves 4
Joshua Bowden hit all four goals as Lincoln United Reserves inflicted Gainsborough’s fourth defeat in the last six games.
Playing against the wind in the first half Lincoln went behind to a 15th minute strike from Craig Lill.
But they bounced back to take all three points with Bowden’s four-goal haul.
Greg Andrews was Town’s other scorer.
Grimsby Borough Reserves 1 Skegness Town 6
New signing Stefan Melin gave Grimsby the lead midway through the first half, but Borough’s joy was short-lived as Liam Parker headed the seasiders level.
Brother McCauley Parker fired the Lilywhites in front as half time approached, but a great diving save from Richard Lovelace to deny Gary Nimmo maintained the lead for the visitors.
McCauley Parker slid in to convert Josh Bartlett’s cross early in the second half and substitute Josh Clarke grabbed his first for the club to make the score 4-1.
Jamie Epton added a fifth when he burst into the home penalty area to fire past Leigh Cook, and Liam Parker rounded things off with his second of the day.
Hykeham Town 2 Boston United Reserves 1
Steven Mehta netted his eighth goal of the season as Hykeham Town won the top of the table clash at the Memorial Playing Field.
Cameron Robertson chipped in with his first of the season to put the brakes on the Pilgrims’ title charge.
Boston’s Lee Orrey was on target with his 12th of the season, but it wasn’t enough to stop United slipping to defeat.
Skegness United 4 Heckington United 0
A brace of goals from Kurt Crossley helped Skegness United to three points at home to Heckington.
His first came after just nine seconds as Skegness began the match with the wind in their faces.
Turning round one goal to the good, the seasiders doubled their lead through Jordan Smith and then Crossley headed his second of the game and 11th of the season in all competitions, to give them a three-goal cushion.
Michael Howard added a fourth with ten minutes remaining.
Results: Gainsborough Town 2 Lincoln United Reserves 4; Grimsby Borough Reserves 1 Skegness Town 6; Hykeham Town 2 Boston United Reserves 1; Skegness United 4 Heckington United 0.
Postponed: CGB Humbertherm v Sleaford Town Reserves; Cleethorpes Town Reserves v Ruston Sports; Nettleham v Horncastle Town.