I collected those three pieces and they counted toward the achievement.

Which side of the entrance did you find the mushroom on: right or left?

While the event has been active, I have found the Charred Kath Shank, Irritable Bloatgourd, and Nova Blade Rotgut. I don't know about the other three but I can confirm the three I mentioned are able to be obtained during the event.

I noticed that about a week or so ago, and wrote a bug about it. Hopefully, they get around to fixing it soon. This doesn't help you much, I suppose, but at least you know you're not alone.

This is one of the reasons for my initial suggestion, actually. Forced server merges resulted in my losing names for some of the characters I had role-played as for years. My suggestion wouldn't seem reasonable, perhaps, to non-role-players, or players who are fine with words thrown together like "ieatglue," as a random exaggerated example, but to people who have invested time and energy into a persona they created as long ago as pre-release, it means something to have access to those names again which were taken from them due to reasons outside their control (i.e. forced server merges). I maintain it is not unreasonable to free up names of characters which have been inactive for a year or more. To the person who said they had 170 characters, many of which they had not logged on for years, you strengthen my point. The financial aspect of the argument that you were a subscriber the whole time so why should you lose your inactive character names falls flat when compared to many others of us, myself included, who have been subscribers the entire time as well. Let's set that aside for a moment. In the interest of the community, instead, I would argue that it would be more beneficial to allow active players to use names, than it would to hoard them away to collect dust like a trophy on a shelf. Now, this suggestion would not apply to people who -for whatever reason- have a ton of names and they actually play them. That's just poor luck for the rest of us. Freeing up names which are not being used harms no one, and could bring happiness to the active players whose story had been cut short due to server merges, or whose spark of an idea might be dashed from being unable to get a name of a character who hasn't logged in since 2017, perhaps.

I think there should be a policy wherein the names of characters who have not logged into the game for a period of one to two years should be freed up for active players to use. Two years is a more than reasonable amount of time for someone to log back in at least one time. One year might even be reasonable, but I'll leave that up to the developers to decide. Either way, people would have more fun if they were able to get names that are currently locked away for whatever reason. Let's respect the active players in the community and help to prevent them from having names full of ASCII characters instead of letters, because people who don't play this game anymore have a bunch of names taken up. You can treat this just like a server merge. If, for whatever reason, those players log back in again, after a period of one or two years, they can either keep their name - if no one more active has taken it - or be provided with a free name change by the developers. This seems perfectly reasonable to me, and to others I have spoken with in-game about the topic.

I am on the Begeren Colony server and have the same problem with Alderaan. I haven't tested the other planets yet. I'm able to travel to Alderaan just fine on the Ebon Hawk server, though.