designFilt error ONLY inside function

I'm using designFilt to make a simple bandpass filter for some data before doing further analysis:     myfilt = designfilt('bandpassfir','FilterOrder',20, 'CutoffFrequency1',0.1,'CutoffFrequency2',7, 'SampleRate',128); If I run this line directly in the command window, it works just fine. (In my old scripts it worked fine too.) However, when I call it from inside a function embedded in a larger script, I get this error:   Error using designfilt>parseAndDesignFilter (line 516) Incorrect dimensions for matrix multiplication. Check that the number of columns in the first  matrix matches the number of rows in the second matrix. To perform elementwise multiplication, use '.*'.   Error in designfilt (line 224) [err,requestedResponse,parseParams,h] = parseAndDesignFilter(inputParamValueNames, varargin{:});   The code (inserted above) is literally copy-pasted from the script, so I cannot figure out what the difference is. I've tried making sure that the "myfilt" variable is cleared each time the function is called just in case there was some problem there. It has no effect. I don't even know what to try next. Any suggestions?