Ruined our wedding.
We had booked two apartments to stay in for our wedding, which Constantin had confirmed a few months prior to our booking. On the morning of our wedding he told me that only one was available due to Airbnb's system causing a booking error. From our side, there was no error from Airbnb - we had two booking confirmations, two receipts following the payments been taken etc. I think it was Constantin who made a mistake and didn't own up to it, or apologise.
Constantin told us that he could only provide us with a double bed flat, and that there was no alternative accommodation available. This wasn't true as we had found another one of his properties listed on Airbnb as available on the dates that we needed and asked him if we could stay in - he did not reply.
His lack of communication was poor, which caused a lot of stress.
I would not recommend staying in one of his properties.