Am so frustrated and disappointed that no-one at BA can see why so often I am unable to check-in on-line and sometimes unable to choose seat after booking - a great boon for Silver Exec status which I value.

Last year, for ~6 months, I was often unable to check-in on-line for Heathrow outward flights.

Got so frustrated I complained on-line, over phone and even in person to BA customer services rep in lounge (very pleasant but weeks later he couldn't get a clear answer). Anyway, confirmed nothing wrong with me, my account, profile or anything and things seemed to return to normal.

Three weeks ago I booked code-share flight out of Heathrow to Tokyo Haneda - code-share BA/JAL on 22nd April - operated by JAL - booked via Expedia.
Could NOT choose seat with BA web site OR JAL ("passenger not recognised" even though they use same 6 digit ticket code!) and when I phoned both airlines they either directed me to the other company OR said there was nothing they could do and could/would not help me choose seat!

Get to T3 LHR check-in who give me some cock and bull story saying "the emergency contact info you entered corrupted something" BUT I DID NOT enter any such information!
(The only such information could either have come from Expedia or my BA Exec club account - both of which I've checked and see nothing wrong!).

It is EXTREMELY irritating and frustrating knowing one is going on a ~12 hour flight, can't choose a seat yet I'm a regular BA traveller to Asia (8+ times a year!).

Does ANYONE else have any advice or experiences like this? Is it Expedia? Or the code-share? Or IT systems? Or me!!!?

I am a life-long UK national, UK born, UK passport with no security or criminal records issues! (Yes - I was once asked if I might have some security flag against my name as they couldn't see that time WHY I couldn't check in on line!