Customer Balance incorrect on Cash Receipts Entry

When in Cash Receipts Entry - the customer balance on the header tab does not always show the correct amount. Mostly seeing it show 0 even though there are open invoices for that account that have a balance on it. Not all accounts and it seems to be random. 

I see the knowledgebase article here: https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=17964&sliceId=1&isLoadPublishedVer=&docType=kc&docTypeID=DT_Article&stateId=15693&cmd=displayKC&dialogID=559227&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl&openedFromSearchResults=true 

but it seems like this is either when receiving an error (which we are not getting any errors) OR if the balance for an invoice on the lines tab displays 0 or is incorrect (which all of the invoices display when on the lines tab and have the correct balance) yet the Customer Balance on the header still displays 0

In the AR_OpenInvoice table , the "Paid Today" field is empty for the invoices and the invoice does display a balance. And Automatic Recaluclate Aging is set to always. 

Sage 100 2017

Thanks for any help anyone is able to advise.