MacBookPro9,2 does not recognize drive as bootable after clean Install
Solution 1:
It turned out the hard drive cable was faulty. I found a couple of Q&A's on the net (like https://de.ifixit.com/Antworten/Ansehen/356610/Hard+Drive+SATA+cable+failing+related+to+the+battery+brackets) that highlighted the issue and so i decided to give a new cable a try. I ordered a new one, replaced it and now everything works without any issues.