Sounds like LCD panel burn if it is really there. Put up a solid light
colored image to verify that it is actually LCD panel image burn. If
it is then the panels need replaced. Might only need one or two of the
panels.

Might be best to try and find same model on ebay that has a lamp
ballast problem and hope it has good panels. Or put it up on ebay with
full disclosure as someone might want it for the lamp ballast or other
parts.