Third-tier Airdrieonians claimed a memorable Scottish League Cup upset with two superb strikes to down Lanarkshire rivals Motherwell.
Last season's runners-up Livingston needed a bonus point on penalties to keep their last-16 hopes alive after being held at home by Raith Rovers.
Dundee are all but through after seeing off hosts Montrose 2-0 for a third victory out of three.
Ross County belatedly kicked off their season with a 1-0 win at Brora Rangers.
Falkirk forfeited their Group E tie at Edinburgh City after a Covid-19 outbreak left the visitors unable to field a team.
In Group F, Motherwell had won their opening two ties but were stunned by Ian Murray's Airdrie in the sides' first meeting for 14 years.
Rhys McCabe's stunning 30-yard free-kick and an unstoppable debut goal from on-loan Hearts midfielder Scott McGill earned derby victory over the top-flight visitors.
It leaves both sides with one game to play while trailing a point behind leaders Queen's Park, who have completed their fixtures.
Livingston salvaged what could be a crucial bonus point as they triumphed 6-5 on penalties against second-tier Raith, who stay top of Group D.
Livingston are three points adrift in third and must beat Cowdenbeath on Saturday to have a chance of progressing.
Dundee went top of Group C with Jason Cummings opening the scoring after the break with a penalty before fellow substitute Luke McCowan sealed victory at Montrose.
Ross County are out of contention for the knockout stage after forfeiting their opening two games following a Covid-19 outbreak. They finally got their season up and running with Alex Iacovitti's header edging out Highland League Brora.