Here's the steps on how to reproduce OP's "issue":

• 1. Create a new wallet or restore an empty wallet (pref. Standard), don't set a password; then close Electrum.
• 2. Go to Electrum's data directory (location) and open 'wallets' folder.
• 3. Open the newly created wallet file as text and under the line "receiving": [ ;
  add these lines: "1JtpgqCf3SSeCeYWEDJjkfYFH7Ruhy4Vp1", and "1FpqQnKQCgDkJFMC94JL8FpRyHTZ3uRVZ1",
  The format should look exactly as the other addresses or the wallet wont be parsed correctly (there's more but I only selected two), then save the changes.
• 4. Open the edited wallet with Electrum and it will show errors, click "Show report contents" on the bug report window and you'll see the error in OP's screenshot. (don't send it as Bug report)
• 5. The wallet will sync just fine and will show the edited-in address' balance.
• 6. Try to send Bitcoins and it'll return with the same error: "Script failed an OP_EQUALVERIFY operation".

Restore the seed phrase and it will not restore the addresses that are edited-in (obviously), it will only restore the keys related to the seed phrase.