Hi,
I'm not able to reproduce the issue on your website:
monosnap.com/file/0xzRNPwbdQugr4ltLi5kTRd18S1RE7
Could you try again and double check that you still have the "invalid token" error ?
Note that this can happen if you wait too long with the page open before clicking on it (basically, if you want longer that the user session lifetime configured in your Joomla configuration). But in that case, you should have the same issue while being logged in, you just need to wait long enough.
For the notice you can just ignore it. It's not related to your problem and we'll add some modification in the future to avoid it.