Timeout during GETDATA with NI 6008 USB DAQ - after repeated use in a function

The Matlab program controls a test rig. DAQ is an inexpensive USB based National Instruments 6008.

The function listed below is part of a larger overall program. It is used to gather bursts of data - typically about 1 second duration. This works well - for a time. But after repeated calls [7 minutes or so], we get the error and the program & rig shut down.

The error is "A timeout occurred during GETDATA".

Any helpful solution would be greatly appreciated.

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%  Function to log real time load and temperature
%  data using a National Instruments USB 6008 DAQ

function logloadtemp(hObject, handles, TimeSampleSec)

LogFreqHz = 100;

DataPoints = LogFreqHz * TimeSampleSec ;

AI = analoginput('nidaq', 'Dev1');
set(AI,'InputType','SingleEnded');
set(AI,'SampleRate',LogFreqHz);
set(AI,'SamplesPerTrigger',(DataPoints+1));
addchannel(AI,1);
addchannel(AI,2);
addchannel(AI,5);
addchannel(AI,6);

start(AI);

data = getdata(AI,DataPoints);

stop(AI);
delete(AI);
clear AI;

averagedata = mean(data);

handles.datadragloadlbsraw = 41.5 * averagedata(3) - 1.6;  
handles.datalinkloadlbs = 1688.6 * averagedata(1) - 316.7;  
handles.datauprighttemp = 2540 * averagedata(2) - 268.1;  
handles.datablockbearingtemp = 2540 * averagedata(4) - 282.1;   

guidata(hObject,handles);