With the recent update, hovering over belts and pressing R now flips them 180 degrees, it doesn't rotate them 90 degrees as it should. Hovering over loaders from another mod and pressing R has no effect, when it should be reversing the input/output direction. Disabling the mod restores the normal behavior. I haven't tested with other entities.

Also happens to inserters and pumpjacks.
And there's something weird going on, if you first "rotate" a belt, and then rotate a pumpjack, it then rotates the pump and the belt at the same time.

I have also run into this. Confused the heck out of me why I couldn't rotate pumps.

Is this with Factorio 2.0 or 2.1?

I'm on 2.0. Pyanodon isn't updated yet. :)

This was an unfortunate edit error. It will be fixed in 2.7.5 (for 2.0) and 3.0.2 (for 2.1)