ok, since yesterday, Rigol representative Jessie Jiang has contacted me. sent me some VI programs to test and clarify some few things to me. it seems most of the firmware bugs i reported has something to do with failure to press or activate "STOP" button or "STOP" command after changing V/Div, S/div etc setting, which seems to be needed to update some internal housekeeping things like preamble returned value, and interleaved memory arrangement.. FWIW, interleaved memory arrangement is used in their WFM file format. but somehow got stucked or leaked into USB stream when "STOP" command has not been activated. in WFM its no problem since we have enough data points as reported on the screen, but leak through USB only half the set.
some people may say, yeah you have to follow the steps, but i say its still less elegant way. housekeeping stuffs should be updated the day we touch setting buttons like V/div, S/Div etc. we dont have to remember to press "STOP" button before rig up the "SINGLE" mode capture. this extra steps can be eliminated in this modern super processing power days, we are not in the 70's anymore. but anyway i give a thumbs up to Rigol for replying back to me, their support team are not that crappy afterall, well but not that stellar either... i've passed my wish to them ie no need to press STOP button to get the right preamble values i hope they listening and make the fix in the next FW update... thumbs up to them.