Help- collapsing yarn cake!

I’m currently having a bit of a yarn winding spree (using a handle Winder and wooden swift) but am seriously struggling with a 4ply 400 m 50% silk and merino. The cake starts ok and then it starts slipping off sideways and pooling at the edges. Is this a feature of the yarn composition? I’ve repeated one skein over and over and it looks a bit of a mess! My Winder has coped with this in the past, including an 800 m of lace! Any tips? I have a picture but can’t work out how to attach it!

Please ignore this post! (I can’t see if I can delete it but it’s a duplicate of another post that I assumed was lost as it was in a moderator queue!)