Went to MBS again today, to try to solve the issue of the mysterious self-puncture of the tubes on my bike. After consulting KS and Joseph and Jai, the reason for the punctures is still unknown.
1) Bad batch of tubes: Possible but unlikely, since the tubes are different (SV6 and SV6A, one bought from CRC and one from MBS).
2) Rim tape: Although the rim tape seems ok, but it might not have been thick enough to stop the tubes protruding through the rim holes. Perhaps the tube has been stretched too much when it was pressurised and squeezed through the rim hole. Possible cause.
3) Overpressurization. Max PSI rated for the Kojak is 95PSI, but that is for the tire. The tube does not really have a max PSI rating. Usually I pump to 95-100PSI, have not had a problem so far for 6 months since I changed to Kojak. Possible reason.
To try to prevent a similar problem from happening again, an extra layer of rim tape was placed on the rim. This made the rim slightly bigger, and it made the mounting of tire really difficult. It was super tight and took a lot of effort and skill to mount the tire. Can't imagine what I would do if I get a puncture. Too difficult to change the tire already.
Right now the tire is pumped to 90 PSI. Shall not go above this next time. Hope the tube holds! It really worries you when the tube can self-destruct when the bike is just sitting at home. Makes you wonder when it will next blow.
The poor man's bike stand. Take care not to damage the rear derailleur!