** English, I just translated all the thread😉**
Eichelober I got exactly the same issue as you last weekend after reinstalling Threema and trying to recover my newest backup (old ones were working fine)
Message was little shorter: "Backup file invalid" in my Android phone, but the solution was as described by jnL. Hereby a short description:
- Backup was made in the SD-card of my phone.
- ZIP File copied to my Windows laptop with USB cable and opened with 7-zip. I got CRC error. Unpack worked.
- Old backup ZIP file copied to the same Windows system and extracted it to just copy the "ballot_vote.csv" to my newest backup.
- ZIP new backup compressed again with ZIP, AES, Deflate and then copied back to the phone with the USB cable.
- Threema Restore started again and Voila!. all GB data are back