Invalid consistancy means, indeed, input and output are inconsistant. This is seen in the Bundle:
This might be caused by a poor/non-functional connection either between lightwallet and fullnode or between fullnode and neighbors. In this case it was between fullnode and neighbors. So the complete and correct bundle was found on the initially used fullnode.
We solved the issue by a replay bundle api call to the initial fullnode and logging the output. We used the output to broadcast the correct bundle to another, functional fullnode by api call sendTrytes. This solved the issue, without any address reuse.
Results are shown in the screenshot below: