I had the reverse problem with Mawson and Davis campaign several days ago. I had a few regular screens with no poly. At first I thought I might have hit the hide poly button but that was not the case. In any event there were no seals to be found and it self corrected so I assumed someone had forgotten the poly on a few maps.
Another issue is that I have seen the Russian outpost twice in M&D and I think once in the Weddell sea campaign. This is the outpost with CCCP on the roof of one of the buildings and the 2 drum shaped structures to the left. Don’t know if the repeat is significant.