If I am reading the code correctly, it looks like the MSTPD algorithm is never downsampling the signal, irrespective of the input sampling frequency, as the variable do_ds is fixed to 0 before being tested see here, this part of the code is apparently never executed.
I have missed peaks (using the provided sample data) for all the beat detectors in the toolbox. Although you pointed out this in your video clip, however I could not find out how to resolve this issue. Could you please explain that.