A Strange "Light Surge" Effect

I've started to notice a strange effect that has happened about 10 times when I photograph falling water drops. After taking many clear, sharp photos of falling water drops during a particular photo session, I will suddenly photograph what looks like a huge surge of light.  Here is an example (the background is a black cloth):

The next photo (and usually the next 4 or 5 photos) will look all dark, or almost totally dark. Here was what the next photo looked like  after I took the photo above:

Then soon things will go back to normal, and I will continue to get nice, sharp details in photos, like the photo below:

I have seen such a thing happen about 10 times recently.  It is as if there was suddenly some enormous surge in the level of light.  Having previously taken many thousands of photos of falling water drops with the same camera, without such an effect occurring, I know this isn't just something you should expect when photographing falling water drops. Maybe it's some strange camera issue, or maybe something spookier.

Postscript: It is now September 14th. I have now observed such a mysterious "light surge" happen at least 30 times when I was photographing, with the effect occurring just as I described it above.