He told me that it could be a problem with the battery holder. It would take some soldering to fix it, but that could result in some damage to the board.

Any idea about this? How much could it cost to have Elektron fix it? And how long would it take?

I was going to buy that OT for 680 €, but now I’m really not sure about buying it at all.

According to you, what would be a fair price for that damaged unit?