This is not only a question but I will deliver the solution as well!
My Breitling Navitimer with the B01 movement was ever so accurate. Losing or gaining one second a day. Now, that I wore it after some time, it lost 5-10s per day!
I had the same problem right after I bought it and brought it to the place where I bought it and the watchmaker said it was magnetized. After I got it back she again was running perfectly.
Now I thought "Let's give it a try and put it on my cheap demagnetizer!" I did that for 5s pulling the watch away from the device while pressing the button.
Now, one day later she is back in perfect shape. Lost 0s in 24h!
Maybe this will help one of you in the future. Sometimes fixes are easy and cheap.
Cheers Alexander