Mac OSX can't load mods: ERROR: Missing central directory

[zaratzara]

I'm playing SRB2 on Mac and it works fine, but I can't seem to load mods. I've downloaded the pk3s for the Chaotix, Sonic Rush & Sonic-R character mods and put them in the default addons folder (/home/Users/{username}/srb2/addons/), and the game sees them fine but immediately errors when I try to load them (screenshots attached). The only error information I can get from the console is ERROR: Missing central directory.

Sonic Robo Blast 2 v2.2.13 (Sep  9 2023 12:16:01 b7f789349 2213-nourl) SDL macOS 64-bit
ERROR: Missing central directory
Errors occurred while loading /Users/barney/srb2/addons/CL_ChaotixChars-v1.pk3; not added.
ERROR: Missing central directory
Errors occurred while loading /Users/barney/srb2/addons/CL_RChars-v1-2.pk3; not added.
ERROR: Missing central directory
Errors occurred while loading /Users/barney/srb2/addons/cl_RushChars-v1.3.pk3; not added.

Any ideas what the problem might be?

Thanks!