I previously saved a couple of node materials which are not there any more. The id’s are “UHAFRK#3” “NF5D79#3” and “20GS7T#4”.
Materials not showing up in this playground
adding @Evgeni_Popov to check
There have been some late changes before the 4.2 release regarding PBR in the node material editor, so if you created your materials before those changes had been made they are not compatible anymore.
Unfortunately, I don’t see any other solution then reconnecting the blocks (the materials are still there in the Materials section of the inspector - one of the material is ok because it does not use PBR blocks).
I see 