Broken boiler so the flat had no hot water for 2 days (and no refund for this!). We were very upset that we couldn't use the shower for 2 days or the kitchen for a day (whilst the plumber installed a new boiler), which ruined our anniversary trip to Barcelona as we were only there for a couple of days. You also need to be careful of the bed - it's a flimsy sofa bed which wobbles/rocks when you turn over in the night, which kept waking us up.
Otherwise the flat is in a great location and was safe and clean.