Ok, some updates: It appears to be a playback only issue but a serious one, I tried the tapes on another Hi8 camcorder and they played well and a tape recorded on that cam played like crap on mine. So I guess recording is not affected.

In the tech service they tried cleaning the head but it didn't work, they told me the headdrum was screwed and I need to replace it. I will try another tech service for a second opinion but I don't expect much.