Hi there,
I have a BV5 (from 2003) and I've never experienced what you are describing - at least I've never noticed anything like that.
What setting levels for brightness, contrast etc. have you got stored...?
I apologize for this not being a very useful response, but theres many people on here that are far, far more knowledgeable than me regarding the technicals, so I hope some can come up with a proper reason/remedy to what you are getting there.
Regards,
Michael
BV5, BV Avant, MX4000, MX1500
BS 7000, BS 5500
Penta III, Penta II, BL 4000, RL 60.2, RL 35, CX-100 Alu
BL 7000, MCP6500, MCP5500, BL 5000, Beo4 (x2), BL 1000 (x2)