Just to put another cat among the pigeons,
Aviation Herald is now quoting "a military pilot" who says he saw the same aircraft, 10 minutes prior to the accident, make a similar left turn that "suddenly" developed into a severe roll and dive, but recovered with high power.
Make of that what you will:
Crash: Ju-Air JU52 at Piz Segnas on Aug 4th 2018, impacted terrain