Approximately how old is the TV?
About 3 years old.
If reseating the ribbon connections did not help, then it is likely that the panel is faulty.
This type of fault is not repairable.
Although the TV is no longer under the manufacturer's warranty period, you may have purchased an extended warranty for it.
If not, you are still covered by your statutory consumer rights which last for 6 years in the EU.
First, try speaking nicely to the retailer and then the manufacturer. They may agree the TV should have lasted longer and offer you a partial refund or credit towards a new purchase.
If they refuse to help, then the 6 year EU consumer warranty will apply: