Yes! I am dealing with the same thing. I have made many phone calls and spoken to the manufacturer of my spa brand. No one seems to want to talk about it. I have tried to get help from my retailer but they just keep saying the exact same thing "it's bio film and you need to adjust your chemicals better." But they refuse to come to my house to evaluate it - even for a fee-which leaves me with the impression they are not being honest. My spa was installed 14 months before this all started.
So what I've been able to find out is the cause is suspected to be the soy based plasticizer the tubing manufacturer changed to in 2014. This manufacturer is in Florida and I am told they supply most (maybe all) of the spa manufacturers so the problem is widespread. But it's a great cover up because no one (manufacturer, distributor, retailer, etc.) wants to be stuck with the cost of remediating it.
Like you I have spent hundreds of hours and dollars on water, chemicals and filters. You're lucky Barefoot has integrity - so far my spa (Four Seasons/Mira) has taken the stand they have never heard of it and have no idea what I'm talking about and by the way don't bother calling them again.
I did get a lot of help from a post on this site by Robbert as well as the maker of a product called Ahh-Some. They've been great. They gave me some instructions for a vinegar/Ahh-Some soak which I've done 4 times now. I've seen a little improvement but the spa is still unusable. I've also emailed a reporter from Pool and Spa News who might write look into it.
I wish more consumers understood that this is not biofilm and that something should be done. The way I see it I have a several thousand dollar paper weight sitting in my backyard.