Audiorecorder object memory limitations / time Shift

Hello! i'm using the audiorecorder object (with recorblocking and getaudiodata), to record sound from an audio device over usb.

I was wondering if there was a limitation of those object (number of samples, sample frequency, buffer...) that could impact performances and quality of the audio (current parameters are 16 bits/48kHz)

in fact i'm comparing the signal (a 1000Hz sinus) acquired in matlab to the signal (the same source) recorded from a reference microphone. Recordings are performed at the same time.

I'm aware that a small time shift of few ms may exist between the two acqusitions (not started exactly at the smae time). However, here is the thing i don't understand : the time shift between my to signals increases during the record !! ...

Is it due to a limitation of audiorecorder ? I tried to reduce the sampling frequency, with no significant effect on the time shift evolution (I'm confident in my reference signals, i'm sure the problem comes from somewhere in the process where the audio is streamed over USB and acquired in Matlab)