Forgot to renew my child’s visa.

We are here on family visas as my husband is Chinese, we have 3 children, and renewed mine and our second child’s visa recently but forgot to renew our eldest child’s in thinking he had a two/three year visa as usual but the last time we renewed it abroad, they only gave a 180 day visa. It just came to our attention that the visa expired 5 months ago!!😩 Do you have any advice or know the penalty for this? I’ve never encountered this situation in the 14 years I’ve been in China. So nervous!