When creating a blueprint with quality weagons and pasting them, i get the following error:
The mod Quality Wagons (1.0.3) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event quality-wagons::on_robot_built_entity (ID 17)
Unknown entity name: legendary-legendary-cargo-wagon
stack traceback:
[C]: in function 'create_entity'
quality-wagons/control.lua:14: in function <quality-wagons/control.lua:1>

I just had what seems to be the same crash. I took a screen shot of the actual error in game if that is helpful.

https://imgur.com/a/ujBCs2c

Same.
https://imgur.com/a/Ii5lO2m