Darrin Bates

Could someone help with the following problem.
I have created some audio backing tracks in Logic Pro X, as I do for all my songs. But when I save these tracks on one certain song, 2 of the audio tracks will not play back.

I have done the following
Resaved the tracks-Failed
Resampled the tracks-Failed
Re constructed the tracks-Failed
Check both files against other files which have been loaded in the uTrack 24 and function correctly

Checked bit rate, sample rate, file ext are all the same
I have deleted all files from the uTrack 24, and reloaded them-Failed
I am completely stumped as to why the 2 track will not play back
Any help would be most appreciated