The Bavarians claimed an astounding 7-2 victory over Tottenham in the Champions League on Tuesday, but failed to retain that clinical edge when faced with Alfred Schreuder's mid-table side in Munich.
Serge Gnabry, four times a goalscorer at the Tottenham Hotspur Stadium, looked to resume that role in the 24th minute when diverting a Joshua Kimmich cross and hitting the back of the net, but the goal was immediately flagged as being offside.
The chance seemed to ignite Bayern as Gnabry struck again, forcing his way down the left wing before cutting in and shooting with his right foot.
Kimmich took the initiative next with a shot that curled over the bar.
He found Robert Lewandowski in the box minutes later, but the Polish striker's header also landed wide of the mark.
The threat of a Bayern goal catalysed a Hoffenheim counter-attack, with Ihlas Bebou taking his chance but finding his shot comfortably saved by Bavarian keeper Manuel Neuer.
The game remained goalless at the break, but Schreuder's underdogs made an instant impact as the second half began.
A handful of chances followed for the home side, before Lewandowski finally managed to convert an opportunity to pull Bayern level.
A cross from Muller was collected by the forward, who then guided the ball past Baumann and into the bottom right corner.
The Hoffenheim response followed just minutes later when Adamyan picked up a cross from Danish winger Robert Skov.
The Armenia international then found his way around Bayern's Niklas Sule before shooting past an outstretched Neuer to claim his second goal for the visitors.
Lewandowski attempted to find an equaliser shortly afterwards, but could not find a gap in the Hoffenheim defence and tried to offload to Muller.
Muller's effort bounced off Baumann, with Sule failing to put away the rebounded ball as his shot cleared the cross bar.
The Bavarians continued to push for a second goal, with Gnabry seeking out Lewandowski who saw another of his efforts sweep wide of the post.
Five minutes of stoppage time was of no use to the reigning Bungesliga champions, who failed to produce an equaliser and eventually registered an underwhelming 2-1 loss.