Wow! that is very strange.
I think @Pneumarian is correct. It is a similar problem to the one with the languages that is only with new installations.
I’m thinking that the programming team are currently working on these bugs that crept into our new release and soon there will be an update released but I’m not too sure if it will only be Linux or will it include Windows, as well: 20200619 Linux Appimage Test Build! - #10 by Frederico
In the meantime, perhaps you can reference the images from the lists here: Measurements - Seamly2D
I have created an issue for this: Measurements Diagrams not available in SeamlyMe in new installation · Issue #273 · FashionFreedom/Seamly2D · GitHub