Reading this thread, I am not surprised of such unscrupulous practice by said vendor.

Here is my opinion (if too long skip to conclusion) which is just an opinion:
Firstly, both parties had agreed before hand that it should take about a year for the item to be fixed. Therefore, the party that had promise to undertake such action should be able to fulfill such request unless the party undertaking such action(seller) has informed the other party(buyer) that the seller might not be able to fulfill such request within the allotted time and that the buyer had consented to the extra time taken. Such was not mentioned, and therefore, there seem to be a breach of contract action.

Regarding the issue of old receipt and that the receipt was not acceptable as there is a change of logo/company name or any change is not really acceptable. One does not absolve his or her liability. To illustrate this issue I would give an example:

Student A rents a house from B. B then decides to sell the house to C. Since A is in contract with B for rent/lease/tenancy agreement and B is not the owner of the house anymore, so what should happen to A? The answer to this is that, when C buys a house from B, he has agreed and consented to any burden that the house is charged with. Therefore, C had taken over the tenancy agreement from B and therefore, A & C should now be in the said agreement.

Other examples, house that has been charged/mortgaged.

They cannot shift the blame to old staff members who are no longer working simply because of the term called vicarious liability. The vendor have to prove that the old staff action is not under their control which is not easy.

I concur that a lot of things can happen within two years, but the statute of limitation for civil cases is six years (general rule).

Conclusion:
Vendor/seller cannot simply absolve liability. They should at the very least replace your item.