This happened at around five hours after airborne, the aircraft start climbing on its own, from FL360 to a max of 47176 feet, while the speed was stable. Then after a short while, the speed was dropped to 152kts from 301kts, as shown in the screen shot below, and the altitude was dropped to 23364 feet.

 

It all happened while I was sleeping, and this was not the first time the aircraft behaving like this. The aircraft's AT was still on CLB when I woke up, and the FPS was really low(5-10 fps).

 

thhis happens to me with A321 .krno-cyvr fl360 an d today egbb-lirn fl350 ones the AC going to crz level the (in APmode) the speed drops an d going in stall.

descending gaining speed and climb agaian slowly and hold speed manual. when reaching descent the AP speed works again normal.

MCDUFPLNDataClb.txt MCDUFPLNDataCrz.txt

to day lkpr-othh  11.32 z taxi-to-crz fine till above turkye fl330 spee M.79 CI 60 at13.17z

speed drops 145kn in AP mode.recover and fly speed in manual mode . until descent the magnenta speed marker is back on the right speed at 16.17z