Toilet bowl effect in RTKFixed

Hi , Any comment this problem ?
I have 2 gps on quadcopter.
GPS - Here GPS
GPS2-Tersus GNSS

When I want fly with RTKfixed drone flies by circling a 2-3 meter diameter but when flies With pixhawk antenna no problem .

The video shows you were in poshold. Does it fly similarly in loiter?

Yes , ı tried loiter but it does not work , not stable…

How do you tell EKF2 to use GPS2 (the one with RTK)?
Do you have autoswitch enabled? Using Blend?

I tried it in two ways;

First: Use Second , GPS2 only

The second: Use best GPS

Blending does not work , ı get message "unhealthy blending "

I am using an F9 u-blox chip and in pos hold and loiter it works really great.
I am not very familiar with tersus chip, i use mine not in nmea but u-blox protocol.

Do you use external and internal compass ? I am using only external compass (on here gps) , may be when it flying second gps , it does not use external compass on gps1 ?

i only load drivers for the external uavcan compass.