I'm trying to set different availability for a date range to some of my services. Every now and then I get the following message when trying to save my settings: "An internal server error occurred. The operation failed." This doesn't seem to have anything to do with the dates as I'm able to set the exact same dates and time slots for some other services. The dates causing the error seem to be totally random and I can't find any reason for this error. Has anyone else faced this issue? Any ideas how to fix this?