In his third season at Den Bosch, where he was the backup goalkeeper, he was suspended for 12 months by the KNVB after testing positive for cocaine – the first player to face a ban for substance abuse in the Dutch competitions.
A subsequent transfer to English club Wolverhampton Wanderers failed to go through due to Aerts refusing to take a drug test.
After some serious mistakes during the 2005–06 season, including a direct pass to opposing FC Twente striker Blaise Nkufo, Aerts benched by head coach Erwin Koeman and in July 2006 he was demoted to the club's reserve team.
[9] He had made his first appearance on loan for Willem II on 3 February 2007, an Eredivisie match against Heracles Almelo.
He made 24 league appearances for the Berlin-based club and was a part of the team reaching promotion to the Bundesliga in the 2010–11 season.