How to prevent ice wall on Medium likeness or less?

[CHEESE!]

I don't have much hope for a reply, but this is frustrating me immensely. On Medium likeness or less, Antarctica can appear as a north-south ice wall on the edges of the map rather than an the northern and southern extremities. This is terribly immersion-breaking for me, and it's annoying to have to regenerate ~50% of maps to roll a good one. Any suggestions for how to edit the map file?

 

[Hive Watch]

I always play random climate and never seen ice wall, but tried temperate today and saw it. Maybe that's the issue?