There is bursts of noise seen in the longer record lengths (1).

Some channels are quieter (2), though all see hints of 500MHz (3).

Channels 6&7 have pick-up that looks very much like 500MHz. (4).

Anyway, there is potentially good news here:

1) we aren`t completely deafened

2) a concurrent EMI baseline subtraction may be possible (use nominally unilluminated channel)

Key will be to see how large signal is.