Coordinate Reference System error while Mosaicing

Hi all,
I am trying mosaicing some SAR images but I get a stupid error which seems to be a bug of the SNAP.

If I select a predefined CRS (in my case EPSG:3031) I get a popup messagge asking me to select a CRS. Which by the way is already selected. I must selet a Custom CRS in order to proceed.

Am I the only one with this issue?