(Shouldn’t there be a bugs/issue forum for stuff like this?)
Just one notification from nearly 4-hrs ago - everything else gone.
(I should add this is in the new, advanced view.)
Back again this morning, thanks.
Correction: they’ve gone again.
All past notifications have disappeared again, but now it seems every time I cause a notification, it deletes the one preceding it, leaving the most-recent one.
They appear to be back again, thanks.