Update: I received the replacement on January 24th, 2019. I am glad that it is solved in the end. So I am going to continure to recommend Pc Byte.
I bought a Corsair K65 RGB Rapid Keyboard from the eBay Store of PC Byte in mid 2017. The keyboard was great for some time and then one key light completely stopped working in November 2018. ( It went dead and alive several times before complete death) I asked them for an RMA number and send the keyboard with extra protections and insurance. They received it and said they have sent it to their supplier and should be back in 2 weeks.
Now it is January and I have sent several mails along with a call to ask them when will my replacement go to me. They simply answered that they did not hear a word from their supplier.
What can I do? It looks like an endless wait. I actually bought quite a few Corsair products from them. If any of them goes wrong I may have another nightmare.
They replied my message on eBay recently saying that the product is old and they have to wait for stock. However the K65 RGB Rapid keyboard is still on sale on their eBay store and their website.
Edit: The keyboard was sent from the store to their supplier in late November. So I think it should be handled even if there is a Christmas period in December.
Its entirely possible with your timeline that their supplier got the keyboard towards then end of December and have been shut down until start of this week and haven't got to it yet + a backlog of rmas have built up in that time.