FJ Software

I want to migrate SMS history from a phone [to be repaired] to an old spare phone (Android 4.4.2).
Since I don't have a valid complete MPE backup of the source phone (which is no longer accessible), only a MPE sms Archive, I tried the following procedure:

• in the source phone MPE profile copy SMS conversations to Archive
  create a new MPE profile for the spare phone
  copy \SourcePhone\SMSArchive.dat to \sparePhone\SMSArchive.dat
  open spare Phone MPE profile -> SMS history is present in Archive
  Try to copy back SMS from Archive into spare Phone: generic error saying this msg can't be copied.

Is it a problem with this procedure ? If so, what are my options (remember, the only copy I have of the original SMS history is in the source Phone MPE profile - no full backup of the phone) ?
Or is it an Android version mismatch ? (source phone = 7.X, spare phone = 4.4)
And of course, I will want to copy back the updated SMS history to the source phone once it comes back repaired.
Thanks for hints

help, anyone ???