When a polyobject rotates, in the software renderer the UVs on one of the sides of each line jitters a lot as it rotates. This can be observed easily in the first level of Hexen, with the swinging doors into the building and the two stone faces which spin and shoot fireballs.

In this case, the texture is slightly misaligned on the side on the viewer's right. Getting a good screenshot of this was surprisingly difficult even with i_timescale 0.1 heh