So Nithral goes into his ice shield but no dogs spawn do go through the stages? is this a bug?

It is a known issue which is caused by corrupt and/or damaged game files. In some cases it can also be caused by badly programmed or obsolete mods. Start by deleting all mods. Then do the following:

If you are playing on GOG Galaxy go to: More --> Manage installation --> Verify / Repair.

If you have downloaded the game manually you will need to download it again and reinstall (you can save your savegames - no pun intended).

The problem should now be fixed :-)