I have a QGIS project (2.18.14 Win10), last saved yesterday, with several PostGIS layers. As I opened the project today the PostGIS layers did not display on the map (but appear in the Layers Panel). The layers' properties (source, etc.) are correct, but their attribute tables are those of other PostGIS layers. It's as if QGIS somehow mixed up the attribute tables.
Other layers (shapefiles) in the same project display correctly.
I have not touched the database. An ArcMap document saved at the same time and accessing the same PostGIS layers shows no issues.
Any ideas on what might be going on and how to fix this?