Having spent the best part of forty years writing and supporting software programs I have had many encounters with “bugs” - the term used to identify errors in computer programs.
I thought that this business would be a welcome change, but I am still meeting bugs and removing them from the work in hand.
35mm slides have a reputation for deteriorating if not stored in ideal conditions. Most opinion blames fungus or mould. As in the first picture, (of a clear blue sky!) this damage looks like some sort of spore.