Crossing China - Vietnam border (Nanning-Hanoi bus route)

Hi everyone,

I will be travelling from Nanning to Hanoi by bus via the Chinese-Vietnamese land border in February. Some websites suggest that foreigners are only allowed to cross the border by 4.30pm / 5pm daily. Can anyone tell me if this is correct? We were intending to take a later bus (the border itself does seem to be open later) and would like to cross after 5pm.

Thank you very much in advance!