For issues you find with the Switch and Console releases, please follow this link and give as much detail as possible. This is the speediest way to get info to Pipeworks and get a hotfix in the works.
1.4 will bring many changes to the PC version. We strongly advise making plans to back up your worlds and players prior to updating your game. More details here.
Begin your search for Journey's End information here and here. Please report bugs and issues for Journey's End here.
For issues you find with the Mobile 1.3 update, please follow this link and give as much detail as possible. This is the speediest way to get info to DR Studios to look at your issue. Also, some troubleshooting hints here.
I've got no readings on the Moon Lord's velocity, but if I'm correct a Lunar or possibly Spooky/Bat/Christmas hook could outspeed him, allowing for melee attacks in the right arena.
This is all on paper.