Thanks for the answers, guys.
The brand I used is this one: https://www.feastwatson.com.au/products/indoor-products/clear-coat/clear-varnish/
An oil-based matt clear varnish.
I think I probably didn’t allow the coat before the latest cure completely, as I did see my sand paper got gummy.
In terms of sanding and reapplying the finish, should I sand the whole benchtop or just around the wrinkles?
@wtnhighlander I wonder what kind of contamination could it be? Something suspicious I can think of, is the mineral spirits remaining in my brush, or the wet cloth I used to cle