Errors when enabling multi process cook.

Hi!
I’m trying out enabling the multi process cooking, using:

CookProcessCount=4

The cook runs ok with this set to 1 but when we use a higher number we start seeing these errors for a number of our assets:

Cook: Content is missing from cook. Source package referenced an object in target package but the object was stripped out of the target package when saved.

I went through the assets and ran the reference validation and resaved them, but it doesn’t seem to have helped (and they build ok with one process).

Can anyone give me some insight on what we might need to change?