Hi,
What does the Asset tracker show? Are the actual texture used in the scene missing from their original location (local for machine A/B or on network drive)?
Are the Out-of-core texture cache locations local for machine A and B or they are on a network location as well?
The usual scenario when managing a scene from different machines is to have all the files and assets of the scene on a shared drive (accessible both for machine A and B) and the out-of-core texture cache location can be a local (faster than network, preferably) drive for the machines.
Do you happen to have the scene assets stored on an online drive (e.g. Google Drive) which is synchronized locally? This scenario is known to cause random asset locating errors.