l-plates

@Racer951: To back you up on this one and hopefully show the headtube is fit for purpose, I use the exact same head tube on my home built DH bike. Supplied by BTR/The bike academy and welded by me. Damn near the exact same head angle as the Pinner too. FEA was done while the frame was still at CAD stage and has had nearly 3 years of DH abuse with no issues. The issue clearly is not the head tube and most likely a combination of the factors already mentioned. (On the FEA point - Anyone that really knows FEA would understand how reducing the support provided to the steerer tube by the upper bearing would increase the stress the mounting of the lower bearing sees).

Something that work well for bearings into blind holes (not many on bikes really but wth) is the tissue paper method. https://www.youtube.com/watch?v=oGRKqkoV4Fw I have done it several times and it removes the bearing with minimal damage, certainly less that a slide hammer will do, the bearing can often be reused as the force is applied evenly and not just to the centre of the bearing.

@johannensc: The problem with a hammer and punch is that your likely to rock the bearing in its bore, ovalising the bore slightly. Not a big issue on a steel frame but Alu or Carbon won't thank you for it and leave you with a poor press fit for the replacement bearing. Granted it works and is done all the time but it is not good practice and in extreme cases can crack the housing. Large bearings on vehicle gearboxes mean the casings are often ruined by well meaning mechanics with a hammer and punch.

A lot of hubs like the novatec and superstar hubs use a round circlip style spring that acts on all the palls at once.