Little advice:
There is a glitchy invisible wall, before ex3 and lower. Inside the house, where is item located, close to exit, you'll get it. Just avoid wall, we accidentally found it with batnik.
There is NO WAY to fix it through stripper (to be honest, I tried), because invisible prop is a brush itself, which is linked with func_wall_toggle entity's with the same names. It will be fixed in next version, sorry for this.