I solved the problem. The picture came at different screen angles, so I figured that it must be the connection issue.

I took the whole PB apart, cleaned all the connections with the contact cleaner and then put it all back together.

I also checked the LCD screen, and it has some electrolytics at the back, but all of them are small radials (through hole) Nichicons 50V unknown value.

Also there is a SMD 100uF 25V cap on the logic board that may leak in the future, but for now I left it there. There are also two SMD caps on the modem board (4,7uF 16V and 10uF 16V), which may require replacement.