Hhmm, so far, I can't reproduce that. But let's get the steps to reproduce really clear.
1 -- 2 instances of Inkscape open (or 2 pre-existing files)
2 -- both have 2 guides, 1 vertical, 1 horizontal
3 -- in one file, 2 rectangles are selected at the same time
4 -- copy
5 -- paste into the other file
6 -- without deselecting, snap to the guide intersection
Are those all the relevant factors?
Of course....Hi Moini! She has a crystal ball, and as soon as I start to type a message, she posts first
I don't understand what you mean. If the objects are on the canvas, isn't the pasting process finished?