Hi,
thank you guys for the explantion. It was completly new to me

Hi Roland, as producers for the big wooden tail units I know Schmepp/Hirth, Deutsche Edelmöbel/Butschowitz and Oberlechner/Spittal.
"Flugzeug- u. Metallbauwerk Wels" is only named as "Reperaturwerk" and I never heard that they were involveld in the K4 production???
Also see the following link:
http://www.geheimprojekte.at/t_wels.html.
Maybe the aircraft was sent there after a manufacturing error occured while the flyover to a near airfield. That wasn't really uncommon to the end of the war.
Matthias