Bryston amp, pop sound at power down.

I have a Bryston 4BSST2 amp that has been wonderful except for a "pop" sound at power down. It is not enough of a pop that I think it will hurt the speakers, but I find it a little annoying. I also worry that it will have a reduced resale value some day as I will have to reveal that fact. 

It is still within the 20 year Bryston warranty period, but when I called a couple of years ago they were dismissive of the issue, stating that it is just the last little bit of power being released, no big deal. 

Does anyone else have an issue with amps making a pop sound at power down? If you did, were you told it was normal? 

Do you knowledgeable electronics people think there would be a way to correct the issue?

I'm debating if I should be more forceful with Bryston. Maybe responses here will push me a bit.

Thanks!