Bad interaction with RTK and GPS?

I’ve been flying a lot with a Pixhawk 2.1 and Here GNSS rtk.
In the last few days I started to add some extra monitoring and safety features.
One of them is that if the number of satellites go under 10 I will hear a buzz.
I do this by using a telemetry link to my computer, which is monitoring the telemetry logs.

That is how I started noticing this.
During a whole flight I hear the buzzer sometimes go off.
When looking at the logs I notice my visible_satellites go to 0 for 3 seconds whereafter it will go back to the number before. The fixtype also goes to 1 temporarily before going back to the fixtype before. HDOP also goes up to 9999.

Now I think this is an interaction with RTK and sometimes not a guaranteed 100% connection and some interaction with the ardupilot code?

Since I have it sometimes, I’m willing to look what is causing this. Does anybody has some pointers where I should look. I have no problems with adjusting some ardupilot code and flashing it on my drone to have more logs or something. Any pointers are welcome.