Compensatory sweating is well known to be a side effect of ETS, and there are a few case reports in the literature regarding facial sweating/flushing. According to some reports, it does seem to be related to a PS/S imbalance as you suggested. Or if that was the primary problem in the first place, the surgery would be considered a failure and you may need re-evaluation. Hope that helps.
Could you direct me to the reports about facial flushing related to imbalance in the S/PS nerve systems?