I've spent a few minutes trying to simulate the thing, after
having whimsically substituted LT1018s for the comparators,
NPN, PNP and PMOS generics for the transistors I don't have
the models for (i.e., all of them), and fixing the values of
some caps and the coils, which seemed garbled.

I don't see what the circuitry involving Q4 and Q5 with the
amplifiers driving them is for either.

The simulation runs without the error you described, but the
circuit doesn't work. I'd say, try to increase the PMOS gate
series resistor to 50 Ohms and/or insert resistors in the
collector leads of the driver transistors. A few tens of ohms
might do it.

I'm sorry but I can't afford to put in the time required to
go any further.

Jeroen Belleman