Audio tracks bleeding !!!

I decided to edit an old Audacity project of 16 tracks, saved about 10 years ago; and to my surprise, sounds can be heard in the background of neighboring tracks as if I were using a multitrack tape recorder. Apart from storing audio tracks as separate files, is there any way to prevent audio tracks in a saved project from leaking?

Your bleeding could be post-Audcaity: e.g. some playback-enhancements which employ crossover between left & right.
If you’re on Windows, check audio-enhancements are off, see …

[ There may also be another layer of similar audio enhancements you should turn off, e.g Dell/RealTek ] .

Thank you.