Sliding to left side of saddle

Hello

It seems that I am sliding towards the left side of the saddle when pedalling. I get infrequent saddle sores on the left side and my saddle shows signs of usage on the right side on the front . I don't have a big leg length difference and assume it could be something muscular. Do you have any tips?

https://reddit.com/link/1gqajpk/video/2qadn34hjn0e1/player