Try this version of swaylock, GitHub - mortie/swaylock-effects: Swaylock, with fancy effects
Download using pacman. I think you would have to remove swaylock to use swaylock effects. This is bascially a fancier implementation of swaylock. It will use the same config file and same commands to do the same things the original swaylock did just with more customization options.
So probably your errors should go away with this.