I could not find the given model, please check the number.
The parts are for a CTX18CISGRAWW which should be a close match.
Replacement parts for General Electric CTX18CISGRWW Refrigerator | AppliancePartsPros.com

Looks like the unit does not have a separate drain pan but uses the unimount bracket (Item 751 in Section 6).

I would pull the unit out from the cabinet, remove the back and check it.
If it is cracked it could be a pain to replace.
Check the drain tube with luck it will be the problem.

If the unimount is cracked I would clean up the calcium deposits and then try to find a cake pan etc. that will fit in the space and install that.

Also a good time to clean/check the condenser coils and fan.
Perhaps the fan is not running and that is why the unimount is nit evaporating off the water. It should be on when the compressor is on.

Take a look at Section 5 in the parts.

By the look of it it runs down the outside back of the fridge.
Probably best to undo and unplug it from Item 315.

If the tubing is clear then it looks like the funnel (Item 226) is mounted at the top of the fresh food section and then it attaches to 315.