When trying to create a Custom Profile Filed trough extension we are using \phpbb\db\migration\profilefield_base_migration class.

The profilefield_base_migration class is created so the user fields can be transferred to CPF. The class has a condition, when creating a lang_name entry for database:

strtoupper(substr($this->profilefield_name, 6))

This way it removes the phpbb_ from field name. As we extend the class for extensions we are not using phpbb_ prefix for CPFs.

Proposing change:

'lang_name' => strtoupper(substr($this->profilefield_name, 6))

To

'lang_name' => (substr($this->profilefield_name, 6) == 'phpbb_' ? strtoupper(substr($this->profilefield_name, 6)) : strtoupper($this->profilefield_name)),