The problem here is that the .nif filenames for the banners don't match their corresponding .kf/nif pair (i.e., TR_act_banner_llothis01.nif vs xTR_act_banner_lloth01.kf). Fixing it should just be a matter of renaming the .nif files in TR_Data.
I also discovered that many of the xnif files have their animation data included (which they shouldn't). They don't seem to cause any problems, but it's still needless file bloat, so I've removed it.

I've uploaded fixed versions of the .kf/.nif files here: http://tamriel-rebuilt.org/asset/fixed-kfnif-files-banner