Heya dude ! Try cleaning all the flatcables ! the laser flatcable and the flatcable that connects the drive board to the mainboard.
Also if you're using a V3 PS2 without the heat pads/HDD bay properly placed, the BAs will heat the DVD drive board and then you will have a lot of broken solders on the board. a lot of weird things like that problem you have might be caused by overheating. So check the heat pads !
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)