When attempting to sculpt on my current project, the center of the mesh distorts, as seen below.
Attempting to use the crease tool on the mesh does nothing UNTIL I get to the center, where the above change takes place. I tried several other tools and I get the same (or similar) results. Let it be noted, too, that I'm using a mirror modifier, and that center seam is where both sides meet, in case that's relevant.
Here is the .blend file, if it helps.

Also a must watch chanels: YanSculpts https://www.youtube.com/channel/UCfjswDVU0XHyBN7UFG0Mi5Q
Zacharias Reinhardt https://www.youtube.com/channel/UCWWybvw9jnpOdJq_6wTHryA
Julien Kaspar https://www.youtube.com/channel/UC77wk1coLw9pXQiFl_Who1A
– Csarb3d Dec 01 '19 at 23:58