A bit of both, you can get lumps or congealed bits in one of the parts and if it's older then the use by date then they don't tend to mix 100%.
It happened to me years ago when I was first making my Japanese walls, the outside got hard like a crust but the middle stayed soft. I poked it a bit too much and it came spilling out of the top. It took a good year or so to go off properly and it now looks like some sort of plant growth on the top of the wall
so it turned our for the best.
There's not that much that I know of that's a cure I'm afraid but some here might. Do you have a photo to show?
It's not for the Arumbaya tug is it
cheers
James