I haven’t got a lite here to check against, but they look like dome contacts to me (like what you’d find in a tact switch)
I can say on a regular switch it’s not uncommon for the dome contacts on the power, vol up and down to tarnish and fail to register. They’re simply covered and held down with kapton tape, in this case you can peel them back and clean the underside of the dome, you can use >2000G sandpaper to polish them up and clean with IPA, you can also use contact cleaner but note, as it’s an oil it will remove any stick on the existing kapton or the replacement kapton unless it’s all cleaned off… and they’ll be good to go again and it’s often faster than switching out the entire flex…especially if you discover this after putting everything back together.
If you manage to identify a suitable replacement for the one in red and instead want to swap it, I wouldn’t see a problem with tinning the pads with lead free and reflowing from the opposing underside of the board. The larger ones highlighted in blue seem to be stuck down with a plastiic (likely not heat resistent) which can likely be peeled up… if i remember right the PSP was similar (or maybe it was Vita)
If you were to find the tracks under the domes is carbon, don’t use IPA near them… it will remove it which is not desired, instead use contact cleaner, or if you haven’t got any standard WD40 should work fine.