The problem with Preview mode not updating as it should has been mentioned before. But my issue is a different variation on the same problem.
I noticed this while working in Foundry and in Skinz. When I change fonts in Foundry’s Typeface stack or in Skinz’ Fontamental stack, the change doesn’t take effect in neither one of these cases—until I switch many times between Edit, Preview and different pages. It seems to work randomly. Saving the project does not have any effect on this anomaly. Even quitting and re-launching RW does not help. The only thing that makes text appear rendered with new fonts is flipping between pages of a project and switching between Edit and Preview on each page, until something “clicks” for no apparent reason.
(MacOS 10.12.6, RW 8.0.3, Stacks 3.6.2. All other addons are up-to-date.)