Unknown Interference

From MetaGeek Friend:

I take dance lessons at a dance school. At each dance nights they
organize, the WiFi doesn't work! The computer is connected to it, but
no access to the Web. I record the following during one of those night.
And then, tada! A BIG spike at approx 2433 MHz. During a dance lesson,
no spike of any sort in this area (I took a record during mine), and so
the WiFi works without a problem. Any ideas of what it could be?

Dance Instruction Interference

I suggested that it may be a wireless microphone as we have seen here:

Bosche Wireless Microphones

She replied,

The problem is, during the dance nights, the wireless microphone is
(normally) not in use. During the dance lessons, it is! Exactly the
opposite of the situation I see on the recording.

Below are the attached files for your ponderance.  Please give our friend Maxime any insight.