I think it has been well enough explained upthread by CWS but I’ll add that one of the lessons I’ve learned from this forum over the years is to first understand those things that need urgent attention (basically everything in the next couple of days or where there is limited service) and when to just leave it to rest (the majority of problems). I have also learned to check bookings regularly which runs the risk of increasing anxiety.

There is a large amount of data in modern airlines that is constantly changing even without disruption and much of the underlying business logic is still set from a time when people were sending bits of paper to each other, typing through carbon sheets and literally affixing stickers. Not to mention the fact that BA and its closest friend AA use different systems connected with bits of string and sticky tape.

That’s not to say BA itself doesn’t have relatively poor IT. During the summer I had a cancellation and tried the online rebooking (I was impressed this was offered at all on a mainly AA operated route). It errored out but I invoked the law of nothing since i didn’t really care much between the options and I had a week to sort it out. The booking refreshed with what I had originally chosen later on.