W900i Dying?

My friend has a W900i which he gave to me to fix. It all started a few months ago when his phone started to act strange and really slow and unresponsive. At that time, he tried everything he could think of, including flashing with SEUS but to no avail. He then gave the phone to me and I flashed it using XS++. All went well, but the phone was still glitchy and acted very strangely and slow. However, it worked and he was able to use it so he was satisfied.

Today, my friend asked me to fix his phone again because now, half of his screen doesn't work, the phone's VERY slow, the camera doesn't work, etc etc. Does anyone know what's wrong or have experienced a similar problem? I'll be flashing the phone tomorrow once the battery is fully charged. The following files will be used:

W900_R5BC004_MAIN_GENERIC_SA_RED49
W900_R5BC004_FS_TAIWAN_RED49

P.S. Which custpack can I use? W900i_CDA102419_23_R4A_Generic_Trade_Hong_Kong or W900i_CDA102419_6_R5A_Generic_Trade_Taiwan? Thanks!