First I would call Haas factory (not the HFO) and ask them to fax you the parameter list for that machine..you will need the serial number. This will be for that machine and that machine only..it will be a list stating how all the parameters where set when the machine left the factory..
Then I would take a hard look a parameters 101 thru 104...these are the "In position Limit" parameters for each axis..101 = X axis 102= Y and so on..(note these parameter numbers might be different for your machine) ..that is why it is handy to have the list from Haas..
There could be other factors too..but I would look here first...as these are directly related to what you have ask about..
G09 and G61 also call "exact stop" with G61 being "Modal"..G64 cancels the G61..so you might try and call a G64 to see if the G61 has been called and not canceled..unlikly but possible..and easy to check.
Also with out seeing the feed rate and code you are running it is hard to say if that is influencing the shuttering..a 96 machine should be a "Brushless" servo machine..depending again on the code it is trying to swollow..it should be good to well over 100 ipm without any shuttering...and as high as 200ipm..but again that would depend on the code, (IE length of small lines and arcs) and the present state of the machine..IE: servo tune, general condition..ect..
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)