Editing table in data view, cursor jumps and loses place

Linux openSUSE Leap 42.1, pgadmin REL 1 20 0, supplied by SUSE repo

I seem to be losing control of my keyboard controlled cursor when 
editing fields in data view in a table.
Steps to reproduce:
1. open table in edit data view
2. table has a string field character varying(150)
3. record contains '/home/colin/vox/athena/wavs/myfile000002.wav'
4. intent is to change 00002 to 00001, for example
5. click in the field to highlight the string
6. attempt to edit 2 to 1, cursor jumps one character, a zero 
disappears, 2 remains
7. attempt to edit other parts of the string such as colin to fred are 
fine, very odd

Just me?
(PS replacing the whole string is fine, so not a blocker)