Nottingham Forest's unease with Stuart Attwell dates back nearly two years to a Championship clash at Bournemouth that was billed as a straight shoot-out for automatic promotion.
Forest stunned the football world on Sunday by saying that because Attwell is a supporter of their fellow strugglers Luton, he should not have been involved in their match at Everton.
Forest were beaten 2-0 but believed they had three legitimate penalty claims turned down.
But Mail Sport can reveal that Attwell's involvement in their 1-0 defeat at Bournemouth in May 2022 was what initially made Forest angry.
With the score at 0-0, Sam Surridge was brought down by goalkeeper Mark Travers – but an incorrect offside call meant no penalty was awarded.
Bournemouth won the game 1-0 and were promoted to the Premier League, with Forest joining them after winning the play-offs.
Steve Cooper was in charge of Forest and said Attwell and his assistant had apologised for the mistake.
'They have put their hands up and owned up to a huge error,' he said.
'It doesn't really help but at least they had the courtesy to own up to the decision that they made.
Attwell was not the on-field referee for a single Forest match in 2022-23, the only Premier League club for which this was the case.
This term, he was in the middle for Forest's 3-2 defeat at Manchester United on August 26.
Attwell issued eight yellow cards and also sent off Joe Worrall in the 67th minute, before giving a controversial penalty for a challenge on Marcus Rashford which allowed Bruno Fernandes to win the match for the home side.