Voice calls always on loudspeaker after Android 6.0 update

Hi,I use Galaxy Tab S 8.4 LTE. I recently flashed Android 6.0.1 (aosp) on my device. After that whenever I receive or answer calls it's automatically on loudspeaker. Toggling the loudspeaker button on the screen doesn't change anything.
Any help please? Thanks in advance

(My first thread)