i've been playing this game for 12 years never knew of a fix for this, even after googling and searching these forums
so you're trying to record a new frag video but your playermodels keep sliding around
1. pause the demo no need to restart it hoping it magically gets fixed
2. set speed to 600
3. quickly unpause then pause the demo again
4. set it back to 100 speed and record without broken walk animations