after upgrade, tracks with loops are substituted

From GB6 to GB10:

When upgrading in 2015 March to new hardware (Mac Mini) and new OS X (Yosemite), my FEB. and JAN. tracks, which used loops, now playback funny sounds, instead of the percussion I had put in.

Q. Why is there synthesizer random notes where percussion used to be?

Q. How do I get my old percussion BACK IN TO those tracks?

Q. From where is GB10 digging up these nonsense sounds?