selecting recorded music span

I am using Audacity on Mac OS X 10.6.8, Audacity was installed from a .dmg file.
Audacity has not been behaving correctly lately.
When I want to export part of a sound file selecting first the start time, then the end time, the latter falls well beyond the selected end time, no matter how many times I try to make it end where I have indicated it should.
This is very annoying, and the only way to overcome this glitch is by manually selecting the span of the sound file I want to export.
This is not an exact way of doing it as it may require to do it as many times as needed in order to get it right.
Please help.
Thank you

How exactly are you selecting the end time?
If you are using the Selection toolbar (, ensure that you have the second box set as “End” and not “Length”.

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