After moving all apps back to the phone, I swapped out the 16 GB and went back to the original 32GB. Didn't reformat yet, or move any apps to the card. Will give the reboot problem a chance to reappear first.
Edit: Same evening, I have now moved the ten largest apps across to SDcard, most of which are games my Grandchildren play :)
Edit: Same evening, I have now moved the ten largest apps across to SDcard, most of which are games my Grandchildren play :)