On the video it looks like the ballscrew is not straight, rather than whipping. If this is the case then no amount of end support change will help this.

Do you have the means to check if it is straight by setting it on some V blocks and rotating it by hand and measuring with a DTI ?

Most ballscrews I have bought are bent and need straightening. You can do it yourself with a hydraulic press but best to send them away to a specialist.