Second Keyboard does not appear.
Could you try the following steps.
Second Keyboard disappears in device rotation.
The keyboard may be killed by system because of memory limitation. For example, when you specify a large image as the background of the keyboard.
Cannot copy images on the pasteboard when tap image keys.
Could you check if Second Keyboard is allowed 'full access'.
Cannot export a keyboard as a email attachment.
Some e-mail provider reject the attachment including '.js' file. Could you try another way such as iCloud drive.
Exported keyboards do not work correctly on a computer.
$xattr -d com.apple.quarantine xxx.zip