Fig.1: On the left table, the selection is not working, but on the right it is.
Both are PostGIS layers from the same server (localhost), and both attribute tables have the option "Move Selection to Top" enabled (not shown on the image).
Using either the "DB Manager" or the "Data Source Manager | PostgreSQL" doesn't change this behaviour.
Both are plain PostgreSQL tables, not views.
On the left layer, If I click a feature in the attribute table itself, it gets selected a few pico-seconds, then the blue background saying it's selected turns back to white. But... If I zoom to feature I have "ghostly" selected, the main screen in centered on this actual feature.
Is the problem known, do I have to tweak something either inside QGIS or PostgreSQL?
QGIS: 3.12.2-București, compile against Qt 5.9.5