thanks Iohannes. it seems the inlets are fine,. and it's just an issue with the outlets, and probably a problem with me not being able to wrap my head around that weird clockwise outlet creation thing, and perhaps also this other issue of pd using the same address for inlets and outlets as an optimisation? it's also very likely to be an error in my code, but i honestly tried everything i could for most of the day, and could not get it working with the outlets running from left to right.
i have now managed to get the external working, by changing the order of outlet creation in tilde_dsp, that makes the outlets backwards.
for the moment, that is fine. but i would like to understand what is going wrong every time i try to use the outlets in left to right order.
am attaching a .zip with the code, the osx pd_darwin external compiled, and a test .pd file.