So what you're saying is that there are duplicate entries recently open list? The wallet file itself is not being duplicated right? Have you looked in the wallets directory to make sure? The directory is here:
http://docs.electrum.org/en/latest/faq.html#where-is-my-wallet-file-locatedI have the duplication in the recently open list on my system too with 3.0.6. A testnet wallet is showing up twice. I think you should file a bug report for that. They should only show unique entries there.
Yes it appends this in the config file:
"recently_open": [
"C:\\users\\***\\downloads\\electrum_data\\wallets\\default_wallet",
"C:\\Users\\***\\Downloads\\electrum_data\\wallets\\Default_Wallet",
"C:\\Users\\***\\Downloads\\electrum_data\\wallets\\Bech32",
"C:\\Users\\***\\Downloads\\electrum_data\\wallets\\default_wallet"
],
default_wallet = Default_Wallet.
I think, as this is Windows, it doesn't cause an error, however, if in linux, there'd be an error if it is on linux (as in Windows "Default_Wallet" as a string in explorer.exe equals "default_wallet").
I'm not sure how this has happened though as it doesn't seem a reasonable thing to have happened.
EDIT:
https://github.com/spesmilo/electrum/issues/4020