Twain to pdf (feeder option ignored)bug?

hello,
somehow the feed option of twain to pdf gets ignored when user interface on false
bug?
if i puth the option on true and select feeder then it works fine ,.... so no driver issue

TwainCurrentSource()
TwainProperty(TwainFeederEnabled,True)
TwainProperty(TwainAutoRotationEnabled,True)
TwainProperty(TwainResolution,300)
TwainToPDF(sRes2,False,TwainAnyType,16,300,0,0,False,True)