Without mesh collider: https://i.sstatic.net/ElIFJ.jpg
With mesh collider: https://i.sstatic.net/4tjtt.jpg (See how legs now walk unpredictably)
Can someone please explain what is the cause of this? Is it colliding with itself somehow? I don't know where to begin trying to fix this.
In case anyone is interested, the gecko setup is from a very cool procedural animation tutorial here: https://www.weaverdev.io/blog/bonehead-procedural-animation
Thank you for any help.
edit: Solved .. ended up being an unpredictable issue from my end (indeed it involved layers). Added my own answer to this which I will accept when it lets me. Thank you so much though for the assistance.
The feet movement was being controlled by Raycasting to Ground layer, but the ground layer was incorrectly set up on my end. This was therefore solved by correcting that issue. D'oh. Now collisions and movement work perfectly. Thank you all.