Doncaster failed to lay their bogey to rest as Dewsbury handed them a fifth successive defeat in their Championship clash at the Tetley’s Stadium.
Despite an error-strewn display, the Dons looked set to claim a losing bonus point until Dewsbury’s man-of-the-match, Anthony Thackeray went over for a 75th minute try.
It was the Dons fourth successive away game and there were clear signs it had taken its toll in a performance which fell well short of their display in the draw at Featherstone.
The Dons had highly-rated Hull FC half-back Jacob Miller on debut as part of the dual-registration agreement between the two clubs, but on the day he and player-coach were second best to the Dewsbury half-back pairing who scored three tries between them.
The Dons looked to have taken fifth-minute lead when winger Nev Morrison touched down in the corner after second-rower Liam Colbon had broken clear down the right before drawing the last line of defence.
The home side hit back strongly and playing with a fluency the Dons struggled to match for most of the game went close on 17 minutes - full-back Dave Scott getting a hand to a try-scoring pass.
The Dons broke the deadlock with a Scott penalty when play resumed following a long break while Russ Spiers received treatment before being stretchered off following a late tackle.
Dewsbury hit back to claim a 4-2 lead with a superb long-range individual try by Thackeray, who defied Scott’s efforts to score in the corner,
The home side doubled their lead in the 13th minute of stoppage time, half-back Kyle Briggs dummying his way over from the last scrum of the half.
The home side increased their lead to 14-2 within six minutes of the restart, centre Callum Beckett forcing his way over from acting half-back for a converted try.
The Dons, who were not helping their cause with numerous handling errors and fell further behind on 55 minutes with a converted try by Shane Grady.
Dewsbury were reduced to 12 men on 58 minutes when second-rower Rob Spicer was sin-binned for a late tackle and they would have suffered another blow had Mike Kelly not dropped the ball over the line.
It merely proved a stay of execution, however, Liam Watts touched down from close range for a 62nd minute try goaled by Scott.