I am not certain, but I worry that search is holding handles and it makes it fail when the user logs back in.
Under roaming really): C:\Users\\AppData\Roaming\Microsoft\Search. I am not sure what is causing it, but make sure that when the user logs off, there are no handles held under this path (or anything It should just be managing the With the new search for server 2019, I have seen some cases where it fails to load when the user logs in the second time. Is it a hard crash or something else? And are you using FSLogix RoamSearch? If not, then FSLogix should not be changing how Outlook and Windows Search interact. I haven't heard of Outlook crashing from Search.