[See solution below]
To move a TYPO3 10 website from tx:gridelements to tx:container I installed tx:container and configured it as it should be. Everything works like a charm. But when I try to move an element (id: 203) into a container-element there occurs an error:
2: SQL error: 'Data truncated for column 'colPos' at row 1' (tt_content:203)
When I then copy the same element and paste it into the container-element it is shown and works like a charm.
[SOLUTION] There was also a module called paste_reference installed and after updating it everything works as it should.