As I mentioned, it is inconsistent, but I am certain it is happening. I would not have chosen the wrong folder several times yesterday Unfortunately, I have rolled back to a previous version.
In sketchup, it is possible that this is being affected by the dialogue for linking proxies or opening textures. If I remember correctly one of the "incorrect" folders that images were going to was a proxy folder I was using. You should try one of those actions between your save operations.