A new update on (as far as i know, only) the x86-64 branch causes this, the original fesiug's edit and the original EPMS to crash. On the original's workshop page I've found a fix posted by a user called @XDforeth this has worked for me and some others it seems judging by the comments

Originally posted by XDforeth:

Hey guys, you may try this method to fix the problem. At least it worked for my gmod (64 bit).
But I don`t know if it will cause potential new problems.

1：Open the following directory of your gmod files:
\steamapps\common\GarrysMod\garrysmod\gamemodes\sandbox\gamemode

2：Find out and read the LUA file called "editor_player.lua"(create a backup for it before we start)

3：Remove the following code(begins at line 271):

concommand.Add( "playermodel_selector", function()

for id, icon in pairs( g_ContextMenu.DesktopWidgets:GetChildren() ) do
if ( !icon.WidgetClass or icon.WidgetClass != "PlayerEditor" ) then continue end

-- We gotta have this at the point of creation for some reason
g_ContextMenu:SetMouseInputEnabled( true )

-- Create the window
icon:DoClick()

-- Make it appear outside of the context menu
icon.Window:SetParent()
icon.Window:MakePopup()
icon.Window:Center()

break
end

end )