Hi, I didn't stumble upon this error but I can try to replicate with my demo site of 17.x - I just need to prepare new db and copy that one over... then I will try the upgrade.
How did you upgrade exactly? (command line vs tiki-install.php vs another way?) Sorry, did not read properly.
PS: also check you do not have any old directories in your upgraded Tiki path like e.g. vendor/ filled in with stuff which was moved to vendor_bundled/ recently...