Keep getting error when trying to process a partial refund.

[Nanxing0]

I have a guest who booked for 83 nights and had to cancel due to plan change. The long term cancellation policy resulted in the first month room fee not refunded (about $1587 on my side) and I talked to the guest we agreed to process a partial refund of $900 first and then if those cancelled nights get booked by others I'll process more. However when I'm trying to process the partial refund it gives me the error "Unfortunately, a server error prevented your request from being completed. Airbnb may be undergoing maintenance or your connection may have timed out. Please try again.". Tried to contact Airbnb customer service by sending them a message 3 days ago but never got any response. Anyone else have the same issue? Weird thing is that I have processed 3 other full refunds for other guests all went through with no issue. Maybe because it's a partial refund and/or the amount is large?