Robert (Lumpy Burgertushie): I salute you and take of my hat deeply. Your solution would have been my second attempt this evening. and I think I would have made it...
I got in touch with a fellow Dutchman (Janus), and he made me do everything all over again. And it did not work. So he came up with the simplest of solutions...For future reference, please put this in a doc file??!!
In the /store/ folder we found 2 files: install_config.php and io_lock.lock. Delete the 2 files, and the installer runs on to the update database. And 2 minutes later I saw
The installer has finished successfully
Take me to the ACP
Successfully updated extension phpbb/viglink
The database update was successful.
a quick peek at the admin panel learned me
Your phpBB installation is up to date. There are no updates available at this time. - Re-Check version
Current version 3.2.0
I don't know where those files were from, and I don't know how they got there. Both are dated TODAY. I am guessing the files are placed there by the installer. I did not put them there, and yes, I deleted the /store/ and copied all new files from the v3.2 installation. And the .zip does not contain those files. I have re-read this entire thread, and nobody mentioned those files.
A big shoutout to Janus for figuring this out !
now a mod may mark this as solved