Taptic engige or antenna replacement?

There is a coax connection on the Taptic unit. The cable incomes around from the case side which you can see in the video in the Apple Watch Series 4 Taptic Engine Austausch guide. So you will need to replace the part and if you damaged the cable end that too.

@jacopocanova you can get those connectors from Mouser.com in Europe as well, This link is for the US site but the same mouser part numbers apply for the european stores. Parts are inexpensive but Mouser is expensive shipping so you may want to shop around any of the major electronic parts store. I believe Farnell in the UK carries those as well.

The Apple Watch Series 4 is nearing iPhone levels of reparability, with the highly-glued display being the primary remaining obstacle. Beyond that, they say the battery is straightforward to replace. Thanks.