Rattled by the niggles, Lash lived up to his surname by lashing out with punches after a fair tackle from reserve flanker Angus Middleton and Winter gave him the yellow card in the 70th minute, leaving the 14-man Buller trapped in their 22m as Wanganui put them away with two more tries.
Middleton was joined by reserve prop Viki Tofa and the returning former captain Roman Tutauha coming on in the 52nd minute, with the game still in the balance at 14-14, and together the trio gave Wanganui a big lift with some strong carries and resolute defence, while steadying the scrum.
Having had a tough tussle with Malneek and the Buller outside backs like winger Illisesa Ravudra and try-scoring fullback Anthony Tailua, Wanganui's midfielders Penijamini Nabainivalu and Kameli Kuruyabaki were now able to take over, with Nabainivalu scoring against his old team mates after a clever kick from Craig Clare.
Clare's remarkable consistency continues to be one of Wanganui's greatest assets, as the try-scoring first-five landed seven straight goal kicks and probed a tiring Buller's weak points throughout the second half.
The veteran earned special praise from coach Jason Caskey.
"He's got it on a string at the moment, you can't understate how important a guy like that is.
"I think he enjoyed having less running to do in the first line than fullback."
Caskey was also pleased with Middleton, Tofa and Tutauha ramping up the tempo, given prior to their arrival Wanganui had found the Buller pack with hooker Anthony Ellis, prop Matangi Ropati and lock Caleb Aperahama a real handful.
"That's what you want with your bench and I've been lucky with what we've got.
"It was one of those games where it's really tricky ones.
"[Buller had] nothing to lose and they came to have a good go at you.
"We were carrying too high and got caught."
Whether he was receiving throws from Tutauha or starting hooker Jack Yarrall, Wanganui lock Sam Madams dominated the lineout with a clean pair of hands, while also getting a couple of steals off the Buller throw and keeping his cool despite some special attention from opposite Robbie Bonisch.
Skipper Campbell Hart was happy for his clubmate Tutauha's return.
"It's great to have him back. He just lifts the team when he's around them."
Hart was ultimately satisfied to finish over the top of their opposition, once the side stopped putting themselves under pressure.
"We gave away three tries in that first half we could have got.
"After a few lapses in the first half we got it together. Can't argue with 45 unanswered points."
The lapses started from the kickoff as Horrocks fumbled a ruck ball and although Buller didn't appreciate the wind with second-five Michael Wells grubber kicking the ball dead, the home side then immediately lost Tafili after an incident at the breakdown just after his surging run from the scrum.
Keeping ball in hand, Wanganui tried to attack from the midfield but dropped some short passes, while a succession of penalties meant Lash could trap them in their 22m.
Flanker Samuel Godwin charged off one 5m scrum, with the ball spread to Malneek, who put Tailua away for another try at Cooks Gardens, with Wells landing a good sideline conversion.
Tafili came back and both he and Kuruyabaki busted the defence, only for the ball to be lost at the breakdown after last ditch tackles near the tryline, and Buller cleared their territory.
Wanganui turning back over hard-won possession inside their half saw Buller spread the ball to each sideline, and although Horrocks pulled off a try-saving tackle, Malneek got the next pass and bulldozed over Rogers-Holden for 14-0.
Needing to be the next scorers but not getting territory, Wanganui caught Buller napping right on halftime as Nabainivalu broke out from his own 22m and fed the ball inside to Kuruyabaki, who in turn offloaded to Horrocks for an open 30m run to the line, giving a chasing Lash the message before scoring.
The visitors had a horror start to the second half when they tried to spread it in their 22m but lost the ball, with Kuruyabaki snatching it and stepping back towards the posts, popping the pass up for Clare to just reach down to place it on the line.
But the momentum stayed with Buller after Malneek probed the defence and then Ellis smashed through it, with Rogers-Holden sinbinned after he prevented the ball coming free.
Turning down three points, the visitors hunted for the tryline but Hart, Nabainivalu and Horrocks contested everything, getting their team out of danger.
The arrival of the reserve forwards finally saw Wanganui take control and never relinquish it, as Tofa and Tutauha took the hit-ups and after Buller missed a lineout throw, Clare fed Middleton to beat three tacklers, with Wanganui soon earning a penalty to make it 17-14.
Another eight phase buildup stretched Buller and Clare's grubber kick out wide was perfect, with no defenders near Nabainivalu and Rogers-Holden, as the former Buller man pulled up to claim it and jogged back towards the posts to give Wanganui breathing space.
The bonus point try followed quickly as Horrocks scooped down to save a loose pass and slipped through the midfield to put winger Cameron Crowley in space, with the veteran showing his classic swerve to beat the sweeper and run 40m to the posts.
Lash's departure left his tired team directionless, and Wanganui worked a couple of penalties into the corner for a lineout – the pack driving off the Madams take as Tofa dived across on the second shunt with Tutauha helping push him over, converted from the sideline by Clare.
A Clare chip kick fell perfectly for Crowley to dash back to Buller's tryline, with reserve No 8 Tremaine Gilbert held up over the chalk.
But after the scrum win the Border boys got together as Madams and Horrocks worked a nifty back-and-forth passing exchange for Madams to dive through the yawning gap to score with less than two minutes left.
Wanganui 45 (Lindsay Horrocks, Craig Clare, Penijamini Nabainivalu, Cameron Crowley, Viki Tofa, Sam Madams tries; Craig Clare pen, 6 con) bt Buller 14 (Anthony Tailua, Robbie Malneek tries; Michael Wells 2 con). HT 14-7 Buller.
