Importing Submissions

I am trying to import submissions as described in https://wordpress.org/support/topic/is-it-possible-to-import-submission/

The submissions are imported, but I have 2 problems:

1. Repeating groups do not seem to work correctly: the fields of the group are simply skipped and all subsequent fields (after the group) are shifted to the left.
2. The first field (Date Submitted) is incorrect (Jan 1, 1970 @ 12:00 AM), if and only if the three letters of the month in the site language differ from the three letters in English.

Can you help?