Preview stubborn - files often open as tabs in a previous window

It has possibly been fixed without carrying out those steps.

I deleted all open documents in Preview and now it appears to work normally. I would have done that before but they were all mixed up in many different tabs. Normally I rename them and file them where needed. This time I put duplicates on the desktop (I didn't want to use their original location) and then closed them all.

Thanks, perhaps that will be sufficient.

That's interesting, but before I do it, the following note.

The computer was recently upgraded from El Capitan to High Sierra. For various reasons, but mostly to save time, whole directories, like Documents, Music, etc. were moved offline. This was done by a professional. However, I did wonder why there are 2 libraries, one under the home directory and one under the user directory.

The priority was to get applications working and this is a machine constantly in action.

Preview was an annoyance but so is Finder, which does not always shows files alphabetically. Both appear abnormal and to me it looks like an OS problem.

Thanks, I rebooted into safe mode, but the problem exists. I repeated re-booting into safe mode again, but no relief.

I set up a tempAdmin account, which appears to work. Where to go from here?

Do you mean putting the OS on an external drive? I already have several attached.

Not yet. It's my media and backups. I'll go ahead with your initial suggestion and see if that works.