the technician that installed the battery likely left the adhesive from a previous or original battery install. this adhesive is also like rolled or gummed up compounding this issue. it also appears like one or several of the following screws are not fully tightened down.
[image|3003722]
make sure these are down all the way (don't use excessive force just check that they are not loose)
also investigate if the frame of the phone is bent. You can do so by laying in back down on a flat surface like a table and seeing if it rocks if when you "tech deck it" reference the image below make sure the camera bump hangs off the edge so there is no high or low spots.
[image|3003752]
fix:
# unscrew and remove the hold down plate for the LCD and battery flex cables
# unplug the battery
# unscrew and remove the face id flex plate cover then unplug it
# unplug and remove the display assembly
# remove the battery
# clean up the adhesive under the battery itself
# replace both screen and battery
# for a guides with details for both processes From IFIXIT linked here [guide|111552|Screen repair guide|new_window=true] : [guide|101279|battery replacement guide|new_window=true]