Hi @R_am
That error means those devices somehow downloaded the same form twice. This is something that happens from time to time but it shouldn't. Could you tell us what ODK Collect and ODK Central versions you are using?
To solve the issue you can try this:
- Go to
Settings
->Form management
and uncheckHide old form versions
- Go to
Delete Saved Form
section (from the main menu) and openBlank forms
tab - You should see two forms with the same version and id just remove one of them.