I have posted this in elektroda.com forum a long time ago.
Using that method you do not need to wait for the new firmware to kick in:
https://www.elektroda.com/rtvforum/viewtopic.php?p=20568836#20568836
Update seems to be OK but after the reboot the old version is shown.
I have to physically take out the smart plug from the wall socket while pressing the button. Wait about 5 seconds and plug it back (and this whole time keep the button pressed) and release the button just after is plugged back in the wall socket. It will show that is running the new firmware after this process.