I had some other problems with the testbuild and modem from 17.09.3:
1.: one spontaneous reboot during the night while charging
2.: the alarm had a strange behaviour one time: when I wanted to switch it off (slide to the right), the pointer stayed at the right, the sound went away but the vibration did not stop. The phone was not responding to any touch, I had to reboot it by long pressing the power button.