SSD USB-internal boot voodoo magic?

[wowzer]

modelamac wrote:
Unless something has changed and I missed the notice, no data is lost by installing an OS over an existing OS. I rarely do a clean installation. Ninety percent of the time I just update the existing OS. I have often re-installed because something did not go right the first time.

[quote=wowzer]
it would seem that the restart/shutdown method still uses the internal SSD as a startup, then switches to the external 'bad' SSD.

How do you reinstall OSX without erasing the user content?

Thanks. I will try to reinstall the OSX. Backing up data first...not so easy as it would seem as I need to get another 10.14.5 volume before i can migrate the user data.