BK 308 Insulation Tester - design error?

[Paul Moir]

Recently I purchased an old BK Precision 308 insulation tester.  I only seldom need a megger so could never justify the price of a new one.  While checking it out, I ran into a bit of an unusual problem:  while it measured correctly on all ranges, the 250V range was only putting out 187V.  BK Precision was kind enough to furnish a schematic upon request, and after tracing it through I found the failure was a partial short in deadtime control pin of the TL594, which is a fancy TL494 PWM controller.  The TL594 is used to generate the high voltage for the 250/500/1000V ranges.
The 308 had been repaired before and while the schematic calls for a TL594, a TL494 is present which makes me suspect that it was replaced before.
Having a look at the schematic, I think I spotted the cause of the failure.   This section of the range switch does two things:  first it sets the reference for the voltage error amp via R1, R2 and Three_Rs.  Second it modifies the PWM dead time via R3.  The capacitor shunted across R3 I think must be to temporarily shut down the PWM when switching ranges.  However I think it generates a negative pulse to the TL594 when VREF when the meter is powered off, the worst being in the middle range.  Normally this pin provides 2-10uA current, and instead mine's consuming ~500uA.
What do you think, is this a mistake or is 4.7uF transitioning from 5v to 0v not really enough to damage anything?  I was thinking about shunting the pin with a schottky.