That project was hell.
It started as a simply Android and IOS apps. So I completed a version which outlined the basic idea that was agreed on along with an API that supported the apps. So once he was happy he paid the first milestone. Then I did go away on holiday for two weeks, I tried to send him an email but I saved it to my drafts by accident - my fault; and his right to be angry at that. We worked it out and agreed to continue. At this point I was waiting on him to provide the designs for the final part of the app. A week later still nothing, so we agreed to go on and have me just put a basic design to it, which I was unhappy about, as it was not what we agreed on, but I continued. Once I was done I went to run the app before sending it to him and it would not show any data...
He had another freelancer working on the site who had completely over written my API. He had no backups. So to make up for my loss of communication before I agreed to redo it for free, a week after agreeing to redo he cancelled the job and left that...
They are all small amounts other than the Karaoke Project, which went so well I have now been building new features for over a year on which is why it is still in continuation.