New painting super brittle

[Laoshi]

I finished a painting a few months ago but didn’t wait the 6 months to varnish and only checked if it was touch dry and not fingernail dry (I did my homework after the fact).

When I crease the unframed canvas even a little or gently rake it with my fingernail it leaves a whiter spot. In some places it looks like only the varnish has been effected, and others it looked like the paint layer has come off with it. It happens on thin and thicker layers of different colors. The canvas seemed to be primed. The matte varnish (of unknown composition, smells like turpentine) has been drying for a month or two.

Any idea on what went wrong and what to do next?