Yes, it’s a known issue. An unfortunately typical problem with Paradox patches: breaking something when they improve other things. They will fix it, probably with a hotfix in the next week.
And checking their forums, there is already a live public beta for 1.6.1. You can manually chose this version in the beta tab from the game in Steam.
From everything I’ve read, I’m already in a live public beta. It’s not my first Paradox rodeo, this one bug caught me off guard when I realized who widespread the issue was last night. With how complex Paradox games are, and how understaffed their QA department seems to be, it’s understandable. Not game-breaking, just weird.
One of their QA guys posts on another forum, and said that there was a new build right before release that broke a bunch of things that were working when they tested it.
Mostly I suspect that the marketing department is to blame; releasing Adams on the anniversary of the release of Stellaris is a marketing-type decision. And that kind of hard, arbitrary release date does have a history of screwing up the work of the people actually developing the game.
The beta apparently has the fix. The list of fixes:
Thank you for this.
I am having so much gun with this game. Does anyone know how to combine fleets?
Select two fleets and press “G”.
There is a button on the UI, top left of the fleet window.
Note, there’s new rules on combining fleets. You cannot combine fleets in FTL cooldown or undergoing upgrades.
Thank you.
The game is great right now, from my perspective.
In my current game, I seem to be the only xenophile in my quadrant of the galaxy. That’ll make things “interesting” after I integrate all the xenophobes into my empire. I’m playing a xenophile, spiritual, militarist empire: enter into our communion of all species, or else. 
I think you can, in the sense that it becomes a queued action that won’t happen until the cooldown or upgrade completes. You can also merge fleets that are in different systems, and they’ll travel to make it so.
That has not been my experience. The UI button is completely grayed out when fleets cannot be grouped.
You are correct! It turns out I was selecting a bunch of fleets and shift-clicking to send them to the same star system. And then later doing the merge.
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It turns out xenophobes don’t like moving from their own planet when they’ve been “integrated” into a multi-species empire. They self-segregate. Although I notice a few dissident xenophile pops of the same species on their homeworld. Maybe they’ll eventually move out.
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On a relatively new colony of borderline habitability, the colonists found some old precursor terraforming equipment. I had the option of dismantling it for minerals or activating it. I pushed the shiny button, because who doesn’t want a better environment? It turns out these precursors were ammonia-based lifeforms. Wiped out everyone on the planet. :smack:
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On another new colony, several years after founding it, I got a call from a Fallen Empire, “hello, you settled on our sacred planet, prepare to die”. I immediately capitulated. No sense wasting effort on a doomed cause. They razed the colony, as promised. And then executed my empress. That wasn’t in the peace terms! :eek:
There will be payback for that one. In two hundred years or so. 
I accidentally annoyed a FE, an isolationist, in my latest game. I honestly thought the two worlds were outside of his exclusion zone, but apparently not. So he declares war and I gather my entire fleet (about 40K at the time) and prepare to defend against his 77K. I did this not because I thought I could win, I wanted to destroy some of his ships to get the debris. It worked. I lost two planets but got some very nice technology.
So decades later, I build up a 125K fleet and escort two colony ships up to the lost worlds and re-settle them. Then I contact the FE and send him an insult. Come at me Bro, see what happens. He attacks and gets utterly wiped out.
At this point, I’ve essentially won. There’s nothing that can stop me from wiping everybody out. I have enough naval capacity to get enough fleet power to stop any crisis. The only thing that could really go wrong is if the Unbidden show up and I can’t hit them immediately but that’s not an interesting enough scenario to keep playing it out.
That’s one of the events with several different possible result; some good, some bad, and one disastrous. You got the latter.
Also, if you lack terraforming tech dismantling the equipment will unlock it for you. However it adds a permanent happiness penalty to the planet.
I feel like a cheater because I eliminated Pirates but they were really ruining my enjoyment of this otherwise awesome game.
Pirates? They are super easy to deal with. even if you’r caught without a fleet, you might loose a few orbital stations, but they always give you time to build more ships before they attack again.
Allow me to add my thanks.
Signed up both myself and my son, we started a LAN game last night. So far, I am digging this game.
This. I finally started keeping a fleet close to the limit, realizing the upkeep costs are not incredibly significant. Pirates are free tech once they pop up. Kill the fleet, trace back to the hideout, send in science ships for research.
Has the fix-it patch come out yet? I got bored being the only aggressive species in the galaxy.
1.6.1 has fixed the no wars but there’s still some serious bugs. One issue is that the AI does not build very efficiently massively overbuilding food and power. The second serious issue it that AI terraforms planets a lot and irrationally.
I’d suggest upping the difficulty level to give the AI an economy boost to balance things out.
However, the game is pretty playable otherwise.
Ok…you guys are right. Pirate file reinserted.
In my latest game I had four anomilies in my home solar system. 
That’s always fun.
In my latest, I’ve started at the very end of a spiral arm. Only hyperlanes are allowed, so I have mine own little corner. Time will tell if it’s stronghold to dominate the galaxy from, or box I’m trapped in.