Nightly: either Pinned tabs or active tabs appear on restart

[lυɒq]

I have a number of tabs kept open for immediate tasks & pinned tabs for returning tasks & when using Nightly recently I lose either the pinned tabs or the active tabs on restart.
This alternates between updates - I'll have either the pinned tabs restored (with no active tabs) or the active tabs & no pinned tabs but what I was last working upon (as if the pinned tab history & the active tab history have branched)

[lυɒq]

update on behaviour - I have not pinned any tabs in the browser for the last few days and with no pinned tabs, upon restarting I just have those active tabs return.
I do not get the behaviour of pinned tabs coming back without active tabs that upon a second restart of the browser lose the pinned tabs and present just the prior active tabs.