Pinned tabs disappearing

My pinned tabs keep disappearing and it's pretty random.

One predictable thing is that they disappear when I "reopen last closed window." But when I noticed that connection, I also noticed that the next new window I opened had all the pinned tabs in place.

Sometimes they just disappear, and no new windows have them, and I can restart Safari and still they don't reappear.

Thank goodness other companies have started building lighter-weight laptops - I am getting so tired of the unresponsiveness of Apple when there's a problem!