The problem report was built with a row set listing the full range of main accounts (+Main = [????], for ease of maintenance), and a column set which included DESC and ACCT columns. Drilling down on the main report page for the account list displayed the account string and correct period amounts, but some of the account descriptions were missing.
The same report run for the prior month displayed all of the account descriptions.
Drilling down on various individual accounts revealed that those not showing descriptions each had only unposted transactions in the current month (for comparison, accounts with both posted and unposted transactions had their descriptions displayed)
When the open batches were posted, the report displayed all of the account descriptions.