Hey there, jumped back onto the game today to start a new play through and was sad to see that this bug still hasn't been fixed. I don't have any mods enabled and it's a fresh install.
So the issue is that every time there is a 2 turn chill effect placed on an enemy, the Ice Fan spell which normally would freeze the enemy no longer does so. So for example if you cast Winter Blast on a target with no magic armour they get a 2 turn chill debuff. If you cast Ice Fan on that target they will not be frozen and instead just maintain the 2 turn chill debuff. Ice Fan itself can still freeze by hitting the target with multiple shards each applying the 1 turn chill debuff as long as no instance of the 2 turn chill debuff has been applied. And both Winter Blast and Hail Strike will properly freeze off of the 2 turn chill debuff. All 3 skills will also still freeze wet targets. The strange thing is that if you hit an enemy with one shard of Ice Fan to apply the 1 turn chill debuff, then both Winter Blast and Hail Strike will freeze the target. So the bug seems to be exclusively Ice Fan trying to freeze an enemy who already had the 2 turn chill debuff on them.
I used to play the hydrosophist build a lot so I know the interactions used to work fine and although you can still play around this bug by always using Ice Fan first in your freeze combos, it limits a lot of the versatility and does not feel intuitive when the skill should be freezing properly. If anyone else is having/not having this bug please let me know. Also if anyone knows of a fix that would be greatly appreciated!