The diffraction spikes you see are not from pinching, but from the lens spacers, and is a common problem. Look at the first image, and you will see three, almost wegde-shaped shadows aiming towards the center of the star, equally spaced 120° apart, and each with two diffraction spikes. This is a tell-tale sign of diffraction from lens spacers. Pinched optics look quite a bit different, with a deformed image, often triangular or elongated. The faint star is perfectly round in the first image, clearly telling that this is not pinching.
Another tell-tale sign that this is not pinching, is that stopping the lens down will NOT solve the pinching, unless you stop the lens so far down, that it's no longer visible, because the resolution is now so poor, it's hidden under the spurious disk of the star.
Thanks for your analysis! I'm pretty sure the spikes are due to the 3 sets of 3 grub screws on the wall of the lens cell (hence 12 screws in total), also spaced at 120 degrees apart from one set to another. I have once opened the lens cell, yes, I opened it, and saw nothing between the triplet lenses but 2 thin metal rings, nothing protruding into the optical path.
I did try loosening the said grub screws to see the spikes GONE before, but I was so greedy at that time, I unscrewed too much, completely losing the centering of the 3 lenses. Hence, I had to send the scope back to its factory for collimation, centering, calibration - whatever it is called.
These pictures in my post were taken upon receiving the fixed scope. I don't have the guts to loosen the grub screws again to eliminate the spikes ...