I created an account on this site today to post in the hopes that it can help others in this situation. I had success this morning with getting Mazda to cover a large portion of the cost associated with this issue. I drive a 2016 Mazda CX-5 with 55,000 miles on it.
I had the same exact issue as the author of this thread and the same errors as posted in their YouTube videos: red BRAKE! light on dash flashing, P! lit up on the instrument panel, and the electronic parking brake (EPB) lever was flashing. This occurred when I went to get into my car after leaving it sitting for about 2 hours. I hardly ever use my parking brake and had not used it right before this happened.
I drove 0.5 mile home, the car drove fine, and I turned the car off and on again twice to see if the errors would go away. They did not. I took a video and picture of what was happening so I could show my dad and anyone at the dealership. I did a quick internet search and came across this thread. I called my dad and then the Mazda dealership, who told me to take it there so they could check it out as it sounded like the brake system was having some type of malfunction.
I went into my house to change clothes and grab a few things and was inside for about 15 minutes. When I got back into my car and turned it on to take it to the dealership, the error lights were off. I decided to take it to the dealer anyway because I didn't want it to resurface again later and potentially be driving a safety hazard in the meantime.
I went to the dealer, they were super nice and gave me a nice loaner car (2019 Mazda 3) since it is later in the day and they would have to look at it the next morning. I sent the service manager the video of what my car was doing since the error lights were off when I took it in. I went home and scoured the internet, going over this thread and anything else I could find so that this issue is hopefully fixed the first time and for minimal cost. I found out about the TSB related to this issue.
The service manager called me this morning and told me the EPB module needs replacing and it will cost me $700 after tax and all. I had read this thread so I was not surprised. I am a college age female and I think I might have surprised him with my knowledge about the TSB and asking him if the rear brake calipers showed any sign of dragging as this seems to be a common issue with the 2016 CX-5's. He told me that they were checked and did not show any signs of that, and reiterated that it is the EPB module that needs replacing due to whatever came up on their "tree" that they plug into the car to diagnose issues. He also told me there were no TPBs out for this issue. I didn't argue with him, but it makes me think that this dealership might not be aware of this problem. I asked him what the risks are for this problem and he told me that it could A. result in the parking brake being stuck "on" and leave me needing to get towed, or B. the EPB could engage at any time while driving, which creates a safety issue. He was very nice and I told him I would call my dad and get back to him.
Instead, I called Mazda's Customer Experience number and spoke to a very nice man. I told him that I love my car, haven't had any issues with it since I bought it last year, and have recommended it to family members. I told him about this problem, how the dealership had given me great service and a sweet loaner, and had quoted me $700 to replace the module. I told him about the TSB that might be related to my problem, and how the dealership told me themselves that my car's problem creates a safety issue. I emphasized that one of the primary reasons I purchased this car was because of its safety, and asked if they would be willing to cover even a portion of this expense since it creates a safety hazard. My car is out of the general warranty, but he was happy to help, called my dealership while I was on hold, and then got back to me in minutes saying that Mazda would cover a large chunk of it, and I only have to pay $143. I was so happy!
Before I was even off the phone with the Mazda rep, the service manager from the dealership had texted me saying they were ordering the part.
They are installing a new EPB module. Hopefully this solves the issue. It appears to have solved the issue for the author of this thread, and hopefully it fixes my problem, too. When I go to pick up my car tomorrow, I am going to ask him what happens if the issue recurs again after this new module is installed(fingers crossed that it doesn't).
If you are having this problem, I recommend you call and talk to Mazda customer service, being nice and telling them your situation and how it poses an immense safety risk. I hope your situation can turn out as well as mine has (so far-- we'll see if this is the true fix for my vehicle).
I will try to update again with any new developments. If I don't post again, you can assume that this fix worked.