Leaders Oxford needed an equaliser six minutes into injury-time from Johnny Mullins just to salvage a 2-2 draw at home to a Wycombe side who played almost the entire second half with a man less.
The visitors lost Charles Dunne to a 49th-minute red card but despite that they still looked set to claim an upset victory thanks to a brace from Dean Morgan, whose efforts in the 44th and 59th minutes sandwiched an equaliser from Danny Rose (51).
However, Mullins' last-gasp intervention saved a draw for Oxford which keeps them top of the standings, level on 10 points with Chesterfield, who ruined Southend's perfect start with a 2-1 win at Proact Stadium.
Once again there was late drama as substitute Armand Gnanduillet's header deep into stoppage-time gave Chesterfield the victory after Freddy Eastwood's 68th-minute leveller had cancelled out Gary Roberts' free-kick 10 minutes previously.
Southend drop to fourth, level on nine points with Fleetwood who moved up to third with their 1-0 win at Hartlepool, Jeff Hughes' 16th-minute tap-in leaving Colin Cooper's men stuck in the bottom two with Accrington.
Another match with late incident saw Burton rescue their unbeaten record with two goals in the last seven minutes to earn a 2-2 home draw with Bury.
Albion trailed to first-half strikes from Anton Forrester and William Edjenguele but Michael Symes reduced the deficit before Adam McGurk's last-minute goal levelled things up.
Burton are fifth after the draw on eight points, one point ahead of Newport and Exeter.
Promoted Newport looked set to continue their impressive start with another victory after taking a 25th-minute lead through Chris Zebroski at Dagenham, but the hosts earned a 1-1 draw thanks to Abu Ogogo's equaliser just before the hour.
In an exciting match at AFC Wimbledon, the hosts moved into the top eight after recovering from a 2-0 half-time deficit to beat Scunthorpe 3-2.
Unbeaten Scunthorpe looked on course for a second win after taking a 2-0 lead through Sam Winnall (16) and Chris Iwelumo (31) while seeing Charlie Sheringham miss a 23rd-minute penalty for the home side.
However, AFC Wimbledon battled back in stunning fashion with goals from Michael Smith (62) , Harry Pell (75) and substitute Chris Arthur (87).
At the foot of the table, Accrington slumped to their third defeat in four games after going down to a 71st-minute Jason Taylor goal at home to Cheltenham.
That was Cheltenham's first victory, and there were also maiden wins for Torquay, Bristol Rovers and Morecambe.
Jordan Chapell's second-half double helped Torquay recover from a half-time deficit to claim a 2-1 success at Northampton, who had led through Jacob Blyth's 30th-minute strike.
John-Joe O'Toole hit a 67th-minute winner to earn Rovers a 3-2 win over 10-man York.
David Clarkson's first-half brace put the home side in charge but York - despite seeing substitute Ryan Bowman sent off in the 43rd minute soon after his introduction - drew level with a double from Ryan Jarvis either side of the interval.
However, York were to leave the west country empty-handed following O'Toole's winner.
Morecambe were also celebrating their first triumph as Kevin Ellison's second-half double saw them defeat previously-unbeaten Exeter.
Portsmouth drew 2-2 at Mansfield, with Ben Hutchinson (33) and Lindon Meikle (72) netting for the hosts either side of goals from Andy Barcham (39) and David Connolly (44) for Pompey.
Also, Rueben Reid converted a first-half penalty to give Plymouth a 1-0 win over Rochdale.