Odd diffraction spikes from a refractor

The other night I was framing an image using my 80ED and Atik 314L when I noticed that some stars in one corner of the image had odd diffraction spikes:

I couldn’t see what the problem was at all at the time, and ended up having to take the entire telescope/filter wheel/camera assembly apart to find out. It seems a small sliver of some material (plastic, possibly?) had dropped onto the edge of the objective lens, presumably in a position where not all incoming light from the field of view could make it onto the sensor, thus it only affected stars near the it’s position.

A quick clean off and the artefact completely disappeared the next night. Not something I’ve ever seen happen before.

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