Recurring event not remembered
I have a number of recurring events set up in iCal. Most of them behave as they should, but one in particular that I have set up to remind me to pay my VISA card gives me a problem. Once I know what my payment is going to be I add this to the event as a sole entry. When I come back to the event later the sum that I entered has gone and it shows just the stock entry. I have been doing this for years without a problem but only recently this has started.
I have deleted and recreated the event; renamed the event, but the info that I add to the event keeps disappearing.
MacBook Pro with Retina display, OS X Yosemite (10.10)