Warren Nel’s hat-trick was not enough as another spell of three wickets in three balls sent Spalding to defeat.
A maiden Lincolnshire ECB Premier League century for Lindum’s Will Wright saw them reach 266-6 with the last three wickets falling to Nel.
Spalding then reached 140-4 but then slipped to 165 all out with Ryan Sneddon taking the last three in three balls to win the game for Lindum.
Billingborough were bowled out for 155, but Sleaford were then made to fight for every run before finally scraping home by just one wicket.
At the top of the table, Bourne marched on, picking up another 18 points at Jubilee Park where Woodhall Spa finished on 203-9, Jonny Cheer hitting 50 and Tom Dixon taking five wickets.
Ben Stroud then made 75 for the visitors in their six-wicket win.
Market Deeping’s title hope suffered a setback at the hands of a resurgent Skegness who, after hovering around the relegation zone early in the season, are now eighth in the table and only 14 points off a top-six place.
Sean Chamberlain made an unbeaten 86, Scott Tallott 80 and Paul Butler 56 as the seasiders recorded the day’s highest total of 295-6 before bowling Deeping out for 125.