Is the relevant radiation solar radiation, or is there damage from radiation coming from the direction the optics are pointed? If it's the latter, then maybe the sun's emissions interact with inbound particles from sources outside the solar system? (I don't have sufficient background or time to check whether the paper already rules this out.)

This sounds like the "hmm this is strange" first step of discovery.

you should see what cosmic rays do to space telescopes

public almost never sees what raw images look like

RAW https://blog.galaxyzoo.org/wp-content/uploads/2010/04/spiral...

FINAL https://blog.galaxyzoo.org/wp-content/uploads/2010/04/spiral...

* https://blog.galaxyzoo.org/2010/04/12/how-to-handle-hubble-i...

they also slowly destroy the sensors since they are physical particles moving at almost the speed of light

It's well known that higher solar wind/CMEs density/speed/etc that comes with the peak of the 11 year intensity cycles scatters cosmic rays before they enter the inner heliosphere. Combine this with the 1~3 years it takes for the solar wind to travel out through the heliosphere and you get the phase difference. Really cool unintended sensor empirical data on it though.

Don't try to correlate with the sun spots, correlate with the solar wind/cmes from the spots getting out far enough to effectively scatter the incoming cosmic rays away.