The default behavior of a looper with the fixed length setting, is that the looper will start recording at the start of the pattern until the end. After it has reached the end, the looper will automatically return to play mode.
When using a division of 2 or higher, the looper will remain in record mode after the division end has been reached. It will go into overdub mode and recording has to be stopped manually. Even when the pattern end has been reached it will still stay in record mode.
So when using a division > 1 the fixed length does not properly operate.