"E174: Command already exists" error when installing/updating plugins with vim-plug?

[khughitt]

When attempting to update or install new plugins using commands like :PlugUpdate with vim-plug, I get the following error:

Error detected while processing nvim/plugged/vim-scroll-barnacle/plugin/scroll_barnacle.vim:
line  352:
E174: Command already exists: add ! to replace it

Line 352 appears to refer to the ScrollbarOn call:

command ScrollbarOn call SBAddScrollbar()

I checked and I couldn't find any other plugins that make use of the same command name. Is it possible that that part of the config is somehow being executed twice?

I also tried running nvim with verbose logging, but it didn't provide any additional information.

Any ideas what the issue could be?

Nvim version

NVIM v0.5.0-589-g91572ddad
Build type: RelWithDebInfo
LuaJIT 2.0.5
Compilation: /usr/bin/cc -D_FORTIFY_SOURCE=2 -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -O2 -g -Og -g -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-prototypes -std=gnu99 -Wshadow -Wconversion -Wmissing-prototypes -Wimplicit-fallthrough -Wvla -fstack-protector-strong -fno-common -fdiagnostics-color=auto -DINCLUDE_GENERATED_DECLARATIONS -D_GNU_SOURCE -DNVIM_MSGPACK_HAS_FLOAT32 -DNVIM_UNIBI_HAS_VAR_FROM -DMIN_LOG_LEVEL=3 -I/home/keith/.cache/yay/neovim-git/src/build/config -I/home/keith/.cache/yay/neovim-git/src/neovim-git/src -I/usr/include -I/home/keith/.cache/yay/neovim-git/src/build/src/nvim/auto -I/home/keith/.cache/yay/neovim-git/src/build/include
Compiled by keith@titan

Features: +acl +iconv +tui
See ":help feature-compile"

[khughitt]

@sslivkoff Any thoughts on what might be causing this? Everything else seems to be working well, but I still run into this error.