Some addresses have unconfirmed coins, I used "Freeze" option for those addresses, then I checked "Spend only confirmed coins" in Electrum properties.
Anyway, Electrum sends from addresses including frozen ones.
This sounds like Electrum is including your wallet's "
local transactions" in your new transaction's inputs.
It also can be seen in transaction preview under "Send" tab before the transaction is sent.
If I use "Spend from" the transaction will not be broadcasted and I receive an error something like "Server returned an error, try to select another server..."
This again looks like you've created a transaction using a local transaction as an input then the server returned that error because it's rejected by its node.
I might be rejected because the input was already spent by another transaction or it's just invalid.
Do the icons of those "
unconfirmed transactions" looks like "
three white gears" or a "
computer monitor"?
Because I've been using freeze and coin control function of v3.3.8 and I never found any issue with it.