48k issue 4B display problem etc

hi,, i have a zx spectrum 48k issue 4B with a display issue it has wavy lines in both the border and paper,some colours seem worse than others ie red is bad blue is good, also when it is cold first boot will fail with white border/black paper with a few red lines. re applying power results in successful boot every time will only fail to boot first time when left for a few hours ..could these two problems be linked. it has a transistor composite mod or thought previously had a capacitor composite mod with the same issue.. i have tried everything short of changing CPU ,, ie replaced video encoder,new lower ram module.different ULA,crystals,full re cap,disabling upper ram.it passes ram tests left in sink mode for hours never has any error..checked resistors etc _5v,12v,5v all present ... anybody have any suggestions


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