https://github.com/frappe/erpnext/issues/15886
As described on the Github issue, when typing the name of a Barcode on the Item Barcode page you get client permission errors. These aren’t actually too much of a problem as it’s just a bit of Javascript trying to query the database to see if any Item Barcodes with the name you have typed exist and if so provide an error message. The change is probably due to the restriction of access to child tables to the client.
I also believe this is a Frappe, not an ERPNext issue; the code that fails is in Frappe not ERPNext and I think its just that Item Barcode hits the issue rather than it being an Item Barcode issue.
I hadn’t posted this initially as it led me to a slightly more serious issue I will be posting in another thread…