My website is for events for 40+ community theatres, so most of my entries use repeat. And many of those use the custom dates feature. I have never had a problem with custom dates. The week repeats, where I select what days of the week to repeat the events on, seems to skip the first repeat date, but that’s the only issue I’ve had with repeating events. Entry of all the events would be a nightmare if not for repeat. (I currently have 833 events on my website. mn-act.net)
After you selected the “Custom Dates” option, another field should appear below that. You click in that field and a calendar should appear. From there you just select the dates you want and they should appear in a list under the entry field. Click on the “done’ button at the bottom of the calendar when all your dates are selected. Don’t forget to click on “update” (or “publish” if not already published). I think this feature is amazing and I use it very frequently.
Also remember with any of the repeat options, the series of events are all deleted and recreated when you “update” them. So any customization you made to an individual event, or bookings for any of that series of events will all be lost. I frequently has shows that run Fridays and Saturdays at 7:00 pm and Sundays at 2:00 pm. I create them all in one series, then edit the start times for the Sunday shows individually. If I make a change to the entire series I lose the Sunday time changes and need to redo them.