What would you do?

I received a job offer last Friday & said I would accept. The manager who rang me to make the offer said the offer was subjected to references which is standard. She also said she'll send through a confirmation email.

Later that day she emailed saying she was pleased to offer me the role but also had difficulty getting through to one of my references. I gave an alternative contact detail for both references i had initially given plus gave a 3rd reference in case they needed it.

Now its Wednesday & i haven't heard any progression.... on one hand if there was a problem with my references maybe something would have been said, i would hope anyway or if the offer was retracted (there wouldn't be a reason why that i can see if the offer was retracted)

Should I email to try & find a follow up? Haven't heard anything regarding a start date. Or maybe wait to the end of the week 1st. Possible they got all details they need but paperwork just going through HR or something.

What would you do?