iPhone X problem with iCloud

Migrated from iPhone 7 last week to X

Now having iCloud issues.

After setting up, worked ok

However for 3 nights in row during the night woke to find “verification on screen for iCloud” enter password

would come back with an "unknown error" when putting in password

eventually it would stick

all iCloud functions working ok, then same again next day.

tried restarting - same problem next day

following day signed out of iCloud then back in

next morning - no error message (thought it was all resolved)

however photo stream would not work (sending or receiving)

logged out of icloud, rebooted iPhone

signed back in, now received photo stream from other devices but iPhone not sending to other.

what next ?

ps my iPad is sharing photos to mac fine (and today to iPhone but not vice versa)