dont write off v4 that easy
i just sold 2 year old v4 heavily used 3-4 hours everyday
neo2 for year then messiah from day1 fitted by ct
one thing i have had to do regulary to it is clean it with cd/dvd cleaner one with little brushes on it
dont ask me why but v4 needs doing regulary, my v5 and v7 never need it
sometimes it struglles with exactly same symptons u are describing
but it plays perfectly after a clean
got to be worth a try