Can't find the file, and then it does.

Most well-configured LANs should be no slower than local system drives. Many "halfway" local networks, though, ones based on shared drives or network storage but without any central server or a decent router, can be a lot slower and a bit glitchy in managing sharing. But any time you move files to a remote storage, especially 'cloud' models, many local apps and systems are going to have access issues as they try to resolve file access, take ownership or control, set access locks etc.

In general, you should work with one and only one copy/source/repository of an asset. Systems that blend local and remote storage in the name of sharing, data safety or marketing hoo-ha are going to show glitches like you're encountering as an app tries to figure out which copy of a resource is the one it wants to access and control.

IMVHO, cloud is fine for backup but should never be used for live, primary assets, and most setups that are trying to automatically back up files to a cloud or NAS while they're in use locally are going to have more annoyances than advantages.

Bring your files local for work, and learn to manually or routinely back up those local repositories, but not all at the same time.