csv import deleted values in object's other fields

We imported a csv file with two columns only: object Id and a text type field. After the import we noticed that for the object Ids, other field values were erased; it looks like specifically the number data types were affected. Here is an example of the Timeline activity, where the only imported field was "Rooms (HDB)" and you can see how other fields got erased. We are on self-hosted v1.3.1