Where to find OEM Dali Epicon woofer?

Tweeters burn out far more often. Open up the speaker and see if there is a loose connection with a lead or in the crossover.  If all is good, contact the manufacturer. Lastly, google is your friend.

Since your dealer isn’t responding, you could try contacting Lenbrook if you’re in the US or Canada since they distribute DALI. Their toll free number and email is at the bottom of their website: https://www.lenbrookamericas.com/

Call first and talk to Bill, then send your woofer to Millersound Speaker service for expert repair.  Search A'gon for excellent reviews.

Millersound Speaker Refoaming, Speaker Reconing and Repair Services

If you need a new driver they make their own drivers. You need to buy one from Dali and go through a dealer most likely.