I'm creating an import CSV file for assets for Merchant Center import functionality and it works until I add tags to the import (variants.assets.tags). I also tried the template file that you provide in the documentation but it also failed.
I always get an error:

Row:1  
InvalidField  
variants.0.assets.0.tags must be an array

Import file:

variants.sku ,key          ,variants.key ,variants.assets.key ,variants.assets.name.en ,variants.assets.sources.uri           ,variants.assets.description.en ,variants.assets.tags
   123456789 ,test-product ,   123456789 ,asset-key-1         ,asset name 1            ,https://example.org/product-video.mp4 ,description 1                  ,new; sale; test

In addition, is there a possibility to target a specific asset like attributes? e.g. variants.asset.1.key so that we don’t need a new line for each asset. 

Regards,
Drazen