Thank you so much for trying to solve this apparently curious problem. I did also spend some time in the last days to try to figure out what and why this happens.first of all, this is how we proceed:
a. we compute a formant-filtered sound (white noise)
b. we edit the Temp/formant-1 file generated by AudioSculpt and name it differently (normally, if a mistake is done in changing this file, we get a normal error message), most of my students use TextEdit for this.
c. we cut/paste the last command line in the last window of AS, change only the name of the parameter file, and recompute the processing (here too, if there is a mistake in the syntax, a comprehensible error message appears).
On my computer (OS X 10.13.6), during my last tests, I simplified the formant-3.txt file in order to leave only one formant, and edited it with TextWrangler, and, to my surprise, it WORKED!! I then added the second line, computed, and it worked, until I got back to the original parameter file (which worked), and has been working since…
One a student’s computer, running OS X 10.14.2, however, this technique did not work and he consistently gets the _M_fill error (he edits the parameter file with TextEdit). So, I believe that your supposition is right, it seems something related to the (dirty, hidden) security processes OS X does behind your shoulder.
As you kindly asked for the simple “noise” sound we were using, I attach it below (compressed), but I do not think that this is the problem.
I continue to experiment, if I can reproduce the problem again.
Thank you again.
noise10test.aif.zip (897 KB)