Form factor code 0 is missing a control declaration
Importing a managed solution from version 8.2 (exported as 8.1 solution) to 8.1 fails with the error
Error Text: Form factor code 0 is missing a control declaration
I found a solution after a long investigation. The reason is that the entity definition in 8.2 is different to 8.1.
I removed the editable grids from the source entity and this fixed the issue for me.
Keep you eyes open for similar issues.