I have installed and restored WhatsApp a million times or so when flashing and switching between ROMs.
Last night I tried something funny, and it cost me too much. I tried to install WhatsApp for another number (my phone has dual SIM). While SMS verification was happening, it got registered via my previously registered WhatsApp number.
Now even after I deleted the new no. account, I am still not able to get my old account back. When I give my old number, it doesn’t ask for SMS verification, and goes to local backup directly, but fails there and throws error.
On the other hand, I can verify the account, but cannot restore all my messages.
My messages are quite important.