Weird dividend issue: am I a moron or have Boardroom stuffed up?

So, a weird one here. I sold a parcel of CDM on the ex-dividend date, 8th September, assuming I would still be entitled to the dividend. The contract note from my broker shows a trade date of 8th September and a settlement date of 12th September (T+2 settlement, allowing for the weekend in between).

However, on the Boardroom website, the holding balance change is showing up on 11th September, which was the record date for the dividend, and I haven't been paid a dividend on these shares.

I've always thought that if I sold on the XD date I am entitled to the dividend, and the research I've done today confirms that (I think?).

So have I got it totally wrong, or have Boardroom got it totally wrong? I've emailed them and will call if I can tomorrow. It seems beyond belief that they could stuff up something like this, which is why I'm second-guessing myself...

Has anyone else had an issue like this with Boardroom or another registry?