Yup, it's screaming caustics internally reflecting in something translucent.

Here is a map of the cameras. The one with the lights is "Näset".

The peninsula is at 63.778, 17.040.

I can't see any buildings there but there does seem to be a path/clearing running north to south to the narrowest point of water there.

What does it look like with each frame overlaid on each other? To my mind that should show the spiderweb pretty well, if it is one.

Apologies for not having the capabilities of doing this myself.

Probably not, because it's moving in the wind, which again is the reason for the typical moving reflections.

I see no evidence of wind in the video, nary a breeze.

Sitrec does it. Video Processing, Echo Light, Full A-B Echo

It's small, close to the camera, and just drifting at a very slow speed. Also, the "motion" of the lights is partly just changes in angles causing the IR to reflect off a different part of the silk.

Forget about the lights, Nessie just casually swims through at 02:49:00

I do... the spiderweb is moving past the camera!

But since it would be very close to the camera, and so not moving very fast, given how long it stays in frame. The wind would be very light. So I'm not sure what other evidence could be visible.

Edit: Originally typed on my phone, have fixed typo issues that this introduced.

It takes only the slightest breath of air to float a cobweb.