Olney let a 10 point advantage slip through their fingers, eventually losing 16-31 to neighbours Wellingborough on Saturday.
At one stage, the home side led 13-3, but Wellingborough showed why they are in third place, rallying to turn the score around and leave with the victory.
The sides shared a penalty each in the early stages, before Olney kicked a drop goal to lead 6-3.
Sensing the advantage, Olney had started to make inroads into some weak defending and spread the ball wide to score a try in the corner which was converted.
Wellingborough fought back with a try of their own though just before half time, reducing the deficit to 13-10 at the break.
Olney opened the gap to six points with a penalty in the second half, but Wellingborough took the lead, and never looked back as they ran in three converted tries to complete the turn-around.
Olney stay fifth in the division, 11 points adrift of Lutterworth in fourth, but just two ahead of Market Harborough in sixth.
Bletchley remain top of Southern Counties North, despite having their game with Swindon College Old Boys postponed.
Having played just once since the end of January, their lead at the top of the table is cut to just two points, though chasing Aylesbury have played two more games.
Milton Keynes look set to finish fourth after a surprising 15-21 home defeat to lowly Wallingford.