I had this problem now in multiple assemblies:

The model needs update.
Please rebuild the model to calculate mass properties.

I cannot publish the assemblies due to company policy, but this problem seems to occur randomly. Sometimes opening the possible culprit assembly solves the problem - sometimes it does not. Sometimes multiple rebuilds solve the problem.

Is there anything I should look out for to prevent this? Is there a common mistake that causes this?

I can open each part/assembly & sum up the masses of those manually, but that is a crazy amount of work.

How do you deal with issues like that?