We are running v9 on-prem and are seeing the error message "Value is not an array" pop up in an alert dialog when editing the quantity of a quote item in the Products sub-grid on the quote form.
Debugging the standard Javascript indicates that this is because, when the item is saved with the new quantity, it then tries to set the value of the other fields on the item (presumably to update the total column etc.) As part of this it tries to set the Unit field, but instead of setting it to the expected array of 1 lookup value it tries to set it just to the name of the selected unit.
This looks like a general bug that would affect anyone using this functionality, but as I can't see any other references to it online, are there any more steps I can take to try and prevent this error? Everything about updating the item itself seems to be working as expected, we're just seeing this annoying message appear afterwards.