[GNC] Cannot always over-type, clear selected amounts

[David G. Pickett]

Sometimes GNUCash gets in a mood, and I cannot over-type or delete selected amount fields in a transaction.  I can click aside to deselect and then backspace/delete the digits, decimal and type in the correct number, but I wonder what happened to the usual GUI behaviors?  I run Ubuntu 20.04.2 LTS and GNUCash 3.8b+(2019-12-29) and Finance Quote 1.49, the latest defined for Ubuntu LTS.