I opened my 2015 15" retina today to repaste the thermal paste and noticed upon reclosing the 2 tabs on the bottom don't click into place. I noticed also, that my battery is possibly swollen - on a 2.5 years old machine. I took some pictures for evaluation as I can't determine wheter my battery is really swollen or it just looks like it. I can slightly press on the battery. Is the battery supposed to be completely flat when new? My machine is a desktop replacement and constantly connected to power.