In line 452 of flowdata.py, you warn Non-standard bit width for data segments with the comment # non-standard bit width... Does this happen?.
In the Data File Standard for Flow Cytometry – Version FCS 3.2 (http://flowcyt.sf.net/fcs/fcs32.pdf) page 39 (3.3.38), the example given uses 10 bits. and I have come across a file (not a .fcs but a .LMD) that was encoded using 10bits.
Maybe it would be nice to adapt the function __parse_int_data to manage int coded using 10bits.