Issues with a real estate company regarding the final payment

Good afternoon,

I purchased through Leptos Estates in 2005. I was in dispute over a final payment because they never completed the snagging.

The last invoice they sent me was in 2008 at which time I contacted them to say I was still unhappy as they hadn't rectified the snagging issues.

There has been no correspondence from them regarding this for over 10 years so I assumed they had accepted my counterclaim. They have now sent me an invoice claiming the interest of over 10,000 euro.

Am I liable or is there a case that they have failed to try to recover this amount even if I have to pay interest as stated at the last invoice in 2008?

Leptos claims that we owe them as monies were outstanding even though they haven't invoiced me or contacted me by email regarding this in 10 years.

In that time, I have not changed my email address and have had my post redirected if ever I was not at my home address.

I would appreciate your thoughts.