This sounds like a “blind spot” to me. Are you using a sync cable between the base stations?
Im not sure if this is corrent, but here is my theory based on some testings done in the past. If you dont use a sync cable, the base stations needs to see eachother at all time. If they dont see eachother for a moment, then only the first “A” basestation will track the controllers. Lets say your base station “A” is in front, it will not see your controller behind your back, and it will stop to track it (it disappears).
This problem could happen in case your base stations are positioned too low or incorrectly, and in some cases your head (or lets say a ceiling lamp or something between) disrupts the “free sight” between the base stations.
Using a sync cable, the base stations are always paired and working together, no matter if they see eachother or not. This is why I ended up using a sync cable already 2 years ago, and never stopped doing so. I got much more reliable tracking using a sync cable.
Another theory could be if you have any mirror/window in your room, that creates reflections and causes “blind spots” for the base station(s).
Anyhow, try using a sync cable and see if it helps @yxcxcv !