Blackberry Passport Overheating
I have had the same issue but yesterday I uninstalled TrueCaller and other background active applications and the overheating stopped. I am quite a heavy user and the end of the day today my charge is on 67%. So I guess it is the background applications which cause all these overheating.
For you to decipher this, just go to tour device monitor and check the applications which have been much of the space on the CPU and those ones you need to download and I think the problem will be sorted out. For me I noticed TrueCaller was in 46% of my CPU usage. I got rid of it and my online now is fantastic, speed is awesome.