Hello

 First I want to thank PMDG for amazing product, but I have a couple of problems that just might be my mistakes. First is that whenever I'm beginning to descend after some time Auto Throttle just stops working, as I move my throttle thurst moves with it but AT seems to be engaged and after some time it fixes it self. Second one is that when I disconnect AP on final nose either goes down or up I don't know how to fix it should I trim it correctly? where should I get those values?

 Thanks

I have had this once, i turned off the AP was decsending manually and suddenly the aircraft nosed up and the thrust went to TOGA i had to disconnect AT first

Look up THR HOLD in the FCOM... Not too sure about your ap disconnect issue, probably a controller spike