Impossible to loop audio correctly

I put an audio mp3 in an audio track but it is impossible to loop it correctly: I cannot change loop length, position or clip start or position: the loop is always on 4 measures !!! When I launch the loop from the computer with mouse or space , it’s ok, the length of the loop is as I asked and wanted. I launch it from touchable, the loop turn only with 4 bars !!! ???