There may be a blockage stopping the water going from collection tray into the evaporating heat sink, the tray may have a crack in it, or there may be to much water being generated for the compressor to evaporate.
With the appliance switched off, I would use a cloth to clean the tray dry and check if any of the pipes to\from are not blocked, and use a wire rod to clear any holes which have any debris in them.
There is very little else you can do, other than try and reduce the amount of condensation generated by the appliance, are you sure all the door seals are not broken, and making a good seal around the door?
Does the evaporating tray look like its making contact with the compressor heat sink?
I think the issue is most likely due to a increase in condensation rather than a reduction in evaporation, if you clear out the water, see if it fills back up, as maybe clearing it out will let it keep on top of demand.
What do you have in place to ensure the condensing plate is making contact with the compressor?
Ok ill await to hear back from you.
Considering the fridge seals are fine, it has to be a problem with a insulating panel failing or (more likely) the temperature control in the fridge.
I think you will find the temperature is fluctuating and this is causing the condensation, this may be the thermostat which is starting to fail so not maintaining a steady temp. The thermostat isnt the easiest to replace in this model, as the cables run right back to the control panel, I would suggest you get an engineer out, who can also check the control board and the coolant system.
If you would like me to recommend somone please advise of your postcode.