Converter In-Rush Thermistors etc, UPDATE -4

The probable truth is that the mfg. chose the cheapest components that are available to do the job. Using more capacitors of a lesser value and higher quality increases cost quite a bit. Allowances for board size, number of through holes, and the additional components, raise cost. Also, components are often sized to operate on the ragged edge of electrical tolerance. I'm guessing that your start/turn off regimen is not the cause of failure unless you happen to be a member of some super-hero league that operates at light speed.

Besides changing the thermistor to one of greater capacity, a soft-start circuit cures a lot of ills. Soft start circuit information.