@paul-thornton The timing is rather critical. Couldn't you extend the time window for updating to let's say 30s?
I've had Zadig be a bit fiddly in terms of getting the timing right. Ive not seen it take that long just to build a catalog. certainly not on decent hardware.
On my laptop:
i7 6700k, generic sdd. it was basically instant.
are you seeing high cpu/io usage during those few seconds? (Admittedly it'll be hard to diagnose given the few seconds of time constraint..)