presser foot lifting during stitch

[jollyroger]

I increased the spring pressure but too much and it will mark the leather. Either way, it seems the vinegarroon process changes the density/hardness of the leather. But it won't affect the thread so I'll just stitch before tooling and coloring. 

I finished up the stitch on the belt by hand. I started a new belt this morning with the same exact leather prior to coloring and had no problems, so thank you everyone for pointing me in the right direction.