Hey, there is an app on playstore name keep screen on basically what it does is, it keeps the screen on of ur phone. when this app install on ur mobile go to that app and just click sceen on then whatever u download from playstore this app will not allow ur mobile to go lock and will keep the screen on for always so basically game or some big app will install on ur mobile without annoying u unlikely it was doing before like it stops the download after sometime when screen goes lock. when ur download goes complete just turn off the screen on mode from that app and ur phone will be normal. but when u r doing this try to keep brightness to minimum to save battery. I don't know why a50 or a30 has this problem or is this the some hardware issue but this is the only solution i got from my side.
did u get some better solution than this or tried something else from phone's setting menu?