OK, so I am making a print layout which has two maps, one an inset map with just a skeleton of a line layer and the other is the detail map at higher resolution. In the detail map, I want to show the labels for each arm of the skeleton. For the inset map, I want the labels to be off.
Even when I 'lock layers for map item', the labels still update in the inset map when the map is exported to PDF.
The update preview is set to Cache for both, but I don't think this has an impact of what gets exported.