I couldn't select seats or check in online for my DONE5 ex-CAI last year and that was issued by BA.

It was re-issued 3 times in total I think - the final time being by BA in SCL and it was re-issued as an e-ticket with about 9 segments left, curiously it worked fine then.

Not too sure why Manage My Booking seemed so reluctant to err.... MMB!

YMMV