the probable cause is that you have more than one customer ledger entry with the same document type and no. as in entry 350, and with different signs. To get the cash receipt posted, I’d recommend to remove the Apply-with Document No. for the offending cash receipt line (the same document no. as in Entry 350), do the posting, and apply the cust. ledger entries after the posting. This should work. However, if you have payment discounts involvet, then it’s better to select the entry to apply with the “Apply Entries” function in the cash receipt journal instead.
with best regards