Sony 53'' Convergence issue

Hello guys, does anyone know what causes pico fuse to go out. I had an issue with convergence, after replacing 1 pico fuse on G board and couple (for red color) on D board, TV worked well for 3 days. Last night vertical blue 8004 pico fuse went out. I replaced it again with new one, TV started working again. What could be causing it to go out?  Thank you for your responces.