But Oldcrow seems to talk about the KLM-367 especially :
See : (3rd paragraph)
http://www.oldcrows.net/~oldcrow/synth/korg/polysix/crowlm367/I've also found useful informations on his site about the capacitors,
which confirm yours :
Tip #2 -- Replacing Old Capacitors
There are two types of parts to avoid, however : mylar capacitors and
tantalum capacitors. There are an abundance of these two capacitor
types in old synthesizers, and they should be replaced first
among all the other capacitors. Replace mylar capacitors with
polystyrene or polypropylene capacitors. Use polypropylene capacitors
in the most tolerance-critical areas : oscillator timing capacitors,
tuned filter capacitive elements, and so on. Polystyrene capacitors
can be used most everywhere else for things such as replacement S/H
hold capacitors, op-amp circuitry, etc.
For places where tantalum polarized capacitors were used (The
Prophet-5 had lots of these), replace them with aluminum electrolytic
parts of the same value. Tantalum capacitors have a very low WVDC and
are the first parts to die if voltage spikes make it past the power
supply defeneses. In general, replace old aluminum electrolytics with
new ones. Modern capacitor manufacturing techniques have yielded much
better parts, so take advantage of this. For power supply decoupling
on circuit boards, replace the usually 0.1uF ceramic disc capacitors
with monolithic dipped-ceramic parts. Do the same for other values of
decoupling capacitors in the circuit.
Lastly--and importantly--replace the filter capacitors in the power
supply. These take a lot of abuse from the AC main line and should be
replaced at least once in the life of a synthesizer.