I have no solution, but there's likely to be a lag when using the Tesla app for this sort of thing, especially if you've just opened the app -- it takes a few seconds to establish a connection to Tesla's servers, for those servers to begin pinging the car, for the car to wake up, for the request to do whatever to get to the car, and for the car to respond. Once the app has been opened for a while and the car is awake, it's much quicker, but even that may not be instantaneous, particularly if the relevant network connections (on the phone, the car, and everything in-between) are flaky. Thus, in debugging this problem, I'd suggest focusing on methods of unlocking your charge port that do not involve the Tesla app on your phone, simply because that method adds in too many variables that are unrelated to the car, and many of which are out of your control.
Also, unlocking the charge port normally requires that the car itself be unlocked. In my experience (caveat: I'm in the USA, with a North American-spec Tesla), it used to be that the most reliable way of getting my charge port to let go of the charger was to open a door and then push the button on the charge handle to stop charging. Pushing that button (on both Tesla's proprietary connector and the J1772 used in North America) causes a signal to be sent to the car to tell it to stop charging, and when the car is unlocked, this would cause the Tesla to unlock its latch. My guess is that it would work the same in Europe with the Type 2 connector used there, but I don't know that for a fact. For the past few months, though, my Tesla has allowed me to unlatch the charge cable without first opening a door. This may be an effect of my upgrading my phone; my new Google Pixel 6 Pro works better as a phone-key than my old OnePlus 5t did. OTOH, it's also possible that a Tesla firmware update has made this action more reliable. Either way, so long as I have my phone with me, I can now walk up to the car, push the button on the charge handle, wait about 2-3 seconds, and pull the charge cable out. During that 2-3-second wait, I see the Tesla logo light on the charge port turn on in green and then change to white, as well as a click from the EVSE's contactor and perhaps something from the car's latching mechanism, too. Anyhow, you might want to try what I've just described, both with and without opening the car's door first.
