the 92Hz line disappearing can be related to one of these operations we have done during the restart ( the timing is corresponding):

_ inspection of a compressed air connector leaking air near PR tower (hissing sound maybe slightly changed)

_ disconnecting of a turbo controller on the SR-BS rack (the pump was OFF, the controller was connected to the mains, it includes a cooling fan).

This could be checked during next maintenance break, looking at accelerometers while repeating same operations