I think the issue is that OP is trying to place icons in any place arbitrarily but they keep moving constantly, similar to this thread below:
There's still not a (definitely) known cause to this, and no solution as it appears, but disabling and re-enabling the desktop icons extension should do the trick; you can see how I did it using the command line in this link but you can also use the Extension Manager (you might need to install it from the Software store):
