Recording of your patch, works Ok.
Attached Mp3 file.
Casiotone mt-240 (primitive, velocity can be 0 or 64 only) midicable m-audio fasttrackpro pd 0.47.1 win8.1
Mensaje telepatico asistido por maquinas.
From: Simon Iten itensimon@gmail.com Sent: Tuesday, June 27, 2017 7:03 PM To: Lucas Cordiviola Cc: Pd-List Subject: Re: [PD] legato portamento
it works fine here as well as long as I don't send very fast runs (20 notes per second and more) did you try with fast midi input?
cheers