FBF in AS 11: deleting frames

[exile]

Trying out FBF with a bouncing ball (laugh if you must!). I can duplicate frames and then manipulate points (so the ball squashes when it lands and then becomes round again). To correct spacing, I deleted frame 8 from 30. But now, when advancing along the time line with the arrow key (or when playing back the animation), the frame skips from 7 to 30 (the top frame in the layer list) instead of from 7 to 9. Then it goes to frame 9 and goes on normally. Can anyone explain what is happening here, and above all, how to delete a frame without getting this unwanted wild jump?

PS. Worse than I thought - thinking it was a mistake to delete from the layer list, I deleted it with the minus key. Result: a double frame that arrests the movement just where I was trying to accelerate it. This double frame can be reduced to a single one, but then the neighbouring frame is double. Something that should be easy is turning out to be complicated.

PPS. Another thing that doesn't seem to work is copying objects from one frame to another.

PPPS. Glad to see a lot of people are viewing this - maybe someone will have an answer as more people try out Version 11. I did the tutorial in the manual - that works, at least!