Hi Moritz,
This seems to a known issue using a particular version of HANA Studio 2.01.5 and trying the recovery without using backup catalog, HANA studio appends the "USING LOG PATH" to the recovery statement causing the issue
Please refer the note below that has all the documentation
http://service.sap.com/sap/support/notes/2157184
Follow the note and use the 2 options of
1. Recover using the backup catalog
2. Use the command line recoverSys.py
Hope this helps
Sunil