Deep cleaning equipment after "brett" contamination

You'll have to thoroughly examine your sanitation process. Of course we all think that we're doing it perfectly, but most of us are not. Think about any equipment that might not get sanitized (for example, your ball valve coming out of the kettle -- do you sanitize it before running the wort out of it? Look for things like this)

My hunch is that it's scratches in plastic that are causing you problems. I would suggest replacing plastic equipment. i.e. hoses, siphons, etc. Plastic is much more porous than one might think. Don't throw the old stuff out just yet, but don't use it until your contamination problem is gone. Then, you can re-introduce your (most expensive) old plastic equipment one piece at a time and make sure that your problems don't come back.

It shouldn't be any problem to clean and sanitize your metal equipment with an appropriate no-rinse sanitizer. What you've told us of your sanitation practices sound good, but you'll need to look at the entire cold-side process.

A story from personal experience: I don't think it had yet caused me contamination issues, but for the first year of brewing, I wasn't aware that you could take apart your three-piece ball valves. There is some nasty shit in there, where the ball sits. I now clean it each time I brew.

Clean, sanitize, keep it simple. Infections will happen because of other things in your environment. You could try wiping down all surfaces around which you will be working for a while. That may help. Also you could try replacing equipment which is inexpensive and more likely to be trouble, like stoppers and airlocks.

However, usually your key issue is that this sort of thing will happen from time to time. Usually it can be prevented between batches but you have to be aware that occasionally you have to do more. this isn't quite the same thing but I did run into trouble once with something growing in several successive batches of sauerkraut probably introduced in one of the seasonings in the first contaminated batch. Sometimes rotating equipment to another different fermentation use can be helpful (that's what solved this-- bucket going back to beer/mead and then back to sauerkraut).

Although you could use bleach as a effective "yes-rinse" sanitizer, the chances are the bugs are in your environment, not just the equipment, so you'd have to do this before each brew, which is a bit of a pain.

Last year I had some slight contamination issues, which I later tracked down to my forgetting the correct dosage of Star San. (That's what happens when you take a 2 year brew-break!) But to be sure, I also alternate with iodophor, since I had some on hand. No contamination in the last 4 batches.

You mix 15ml/0.5 fl.oz. iodophor in 5 gallons. Contact time is just a minute, although I usually leave for a little longer. Iodophor is less effective on unclean surfaces, but since you've thoroughly cleaned everything, there's no problem there. Finally, the iodine does stain - I can't really see a change after a few uses, but I know that it will show eventually.