Don't nudge on series enter.

mods/boxes/nodes.lua

@@ -62,6 +62,9 @@ local function register_teleport(name, def)
 
 	-- on_teleport: return true to nudge
 	-- player back off the teleport
+	--
+	-- return true only when displaying a formspec or
+	-- when the player is not teleported into a box
 	local on_teleport = def.on_teleport
 	def.on_walk_over = function(pos, node, player)
 		if on_teleport(pos, node, player) then
@@ -221,7 +224,7 @@ register_teleport("boxes:enter_teleport", {
 					end
 
 					boxes.open_box(player, {0, tonumber(catbox), 1})
-					return true
+					return
 				end
 			end