With the home side holding an eight-point advantage, Leyds dived over in the corner but appeared to lose control of the ball and came up disappointed, spurning the celebrations of his teammates.
Television Match Official Marius Jonker ruled that at no point had there been separation between his arm and the ball, and awarded the five points to the disbelief of the Brumbies.
The Stormers’ other scores came from flank Siya Kolisi and prop Vincent Koch, while the visitors, who had hooker Josh Mann-Rea red-carded 17 minutes from fulltime, got their only score from winger Henry Speight.
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The home side led 9-5 at halftime after three penalties from Coleman in what was a physical but error-strewn first 40 minutes.
The Brumbies’ try came just before the half-hour mark as centre Tevita Kuridrani broke through the stout Stormers defensive line and sent a long pass for Australian Olympic Sevens hopeful Speight to sprint over.
Having conceded seven penalties in the opening half, the Canberra-based side gifted opportunities to Coleman, not least wing Joe Tomane, who was penalised for a shove to the face right in front of his own posts just before the break.
The Stormers lead was cut to one point just after the break when Christian Leali'ifano landed a penalty awarded after a collapsed scrum, but the home side galloped ahead again when they grabbed their opening try.
After a period of sustained pressure on the Brumbies line, Kolisi barged over from close range.
Leali'ifano added another penalty after which the visitors were reduced to 14 players when replacement hooker Mann-Rea, on the field for only two minutes, threw a succession of punches at Stormers hooker Oli Kebble and received a red card on the advice of Jonker.
Coleman took the lead out to eight points again with the resultant penalty. Leyds made the game safe with his controversial score that deflated the visitors, before Koch added a third in the closing seconds.
(Reporting By Nick Said, editing by Alan Baldwin)
