tldr: Reliable design is HUGELY important. You can't just put these things together haphazardly.
"The fact that less than 50% of participants across all devices could follow the labeled instructions without committing a single error provides confirmation that the need for training on the use of epinephrine autoinjectors is still important...The user-centered device design may have a significant impact on correct epinephrine autoinjector use and patient preference."