Digital Foundry:
There's another issue on top of this. Each time we begin a new stage, our leading bro freezes in place mid-motion within the first few seconds of play. The game continues regardless, but player control is suspended for a few frames - bringing the character to an abrupt halt, and making it too easy to perilously mistime jumps at the start of a level. Given each stage lasts between 30 and 60 seconds, it's a frequent enough bug to frustrate, and we hope it's easy to address down the line.

Are you looking for more games to play similar to Chained Together? Power Up Gaming wrote up a list of titles you may enjoy playing through with others.
"It’s time to suit up and join the Bros as the internationally acclaimed side-scrolling run ‘n’ gun extravaganza Broforce is out today as a boxed Standard and Deluxe Edition for Nintendo Switch and PlayStation 4.
Developed by Free Lives and published by Devolver Digital, the boxed Standard and Deluxe Editions will be created and distributed across European specialist retailers by U&I Entertainment." Free Lives and Devolver Digital.

Because... America – f*ck yeah!
I don't remember if you save the world in that game but Urban Chaos: Riot Response was one of the most american games back in the day, I've never even been to the country and that game was still rad.
I really hate how badly optimized this good game is.
Terrible performance. Hope it gets patched soon.
Another Unity game with poor performance, not shocked.
Broforce has problems on PS4? Sounds like a real eye-opener.