The following only on Tails:
I deleted the wallet, installed it back, many times. Tried to fix it somehow, playing around. Now it doesn't show 2.600, not even that damn 1 transfer, like it never happened at all. I still used the same recovery seed for the wallet as before.
You use same seed, but do you know that same seed can generate different types of addresses? In the process of wallet recovery, there is window where is possible to choose derivation path/address type. You need to select same address type on Electrum (Tails), as it is on Electrum (Windows).
If your Electrum (Windows) is legacy type, it starts with
1, for native segwit it start with
bc1, and for nested segwit (p2sh) with
3. Pay attention to this when restoring wallet, this is a very common problem for many users.
I thinks that is exactly the issue now. It generated different address but the one I sent the BTC to, is not included!