Ringtone after ending call

Hi all

I'm having this strange issue with Teams.

My setting is that I have the secondary ringtone active on the PC speaker, and I'm using an EPOS Adapt360 headset.

When calling, all is well, but as soon as I end the call, the secondary ringtone will play again. This confuses me, as the ringtone is playing, but no one's calling me...

What can be the cause of this?