trim not working properly won't trim to bar

can someone help? when I trim the end of an audio file whatever I change it seems it won't trim exactly to the bar it will be just short or long of it. I have tried with snap on and off and also with zero crossing unticked. I have tried making the file longer and then trim by locaters and then deleting the end bit. But still when you zoom in its out by just a little bit. It is super annoying if you repeat or copy by the end of the song it is out of time with the rest :(

Any ideas