Copying records fails with SQL error without any message
I ran into this issue with MySQL running in strict mode and TCA generated from extension_builder.
When an integer column, e.g. l10n_parent lacks the default setting, e.g.
'default' => 0
the copy process silently fails, only in the main log the error shows up, even with DEV settings.
SQL error: 'Incorrect integer value: '' for column 'sys_language_uid' at row 1' (tx_your_table:NEW584946631ecf8679449302) (msg#1.1.12)
AFAIR, TCEmain errors showed up in older TYPO3 versions as a flash message, which would really help in this case to give the user some feedback. Since strict mode is default for MySQL 5.7, these errors will show up frequently with a lot of extensions.
To simulate the error in older MySQL versions, you can set:
'setDBinit' => 'SET sql_mode = \'STRICT_TRANS_TABLES\';',