I’ve been dropped down from gold to silver.
Is this a bug or anyone else seen this?
Not a bug. The new event has only three colors in it. I believe you must be at gold in at least one to make that level. It is entirely possible that you were in gold for one of the other colors in the previous event, which bumped you to that tier.
Ah cool, thanks for the explanation.
Yikes. I just got to gold tier and it is awful. I have not won ONE, I repeat ONE battle in this event over the last few days!! 
How do I get out of gold tier and go back to silver??
get gud. 
I don’t actually know. I just recently had the same thing happen. I decided to go through and master all my cards. I used to be about 9/10 wins in bronze, now i’m closer to 3/4 in gold… but the progression rewards are a lot better…
If you only levelled one colour to gold then as long as you join an event without that colour you will be back to silver. You can check this by tapping the info on the top right of each event on the event page.
Otherwise, there’s no known way to go down a tier (well besides starting a new account lol). If you’re interested, you can PM me and we can see if there’s a way to tweak your decks to help with that win rate.
Here you have an answer:
https://forums.505go.com/discussion/48090
At the end:
If you stop mastering cards, when new expansion arrives maybe you will be moved to silver.
If you stop mastering cards, when new expansion arrives maybe you will be moved to silver.
I think the original point was that when new sets are released they will need to add higher tiers above platinum, and people will naturally move into higher tiers as they play. A week or two after that happens a tier such as Gold effectively becomes like Silver is now as long as you try not to master cards and get pushed up a tier with everyone else