Apologies is this is raking over old coals but my forum search didn't come up with a definitive answer.
 
If I try to copy audio from one take lane to another in the same track, or try to copy audio from another track it seems to fragment the existing data.  Basically moving data between take lanes seems to have very unpredictable results, so is this just something you shouldn't try to do?  Are there some simple hard-and-fast rules about what you should or shouldn't try to do with take lanes?
 
I recently upgraded from 8.5 to Platinum, and I am very aware that things I used to do quickly now require quite different workflows...

I'm still new to this so take it with a grain of salt....
 
The video I watched muted the parts of each take NOT wanted and then I could play the "take" I wanted. I don't remember how to "finalize".
 
What I do remember is having a ton of trouble, as you have, copying between takes. I;m guessing it's not a best practice. I am also willing to say I'm all wet if proven wrong....

Paste is not fully lane aware. It defaults to pasting to the same lane of the same track or the first available (i.e. not already occupied) or new lane when pasting to a different track. To change/control the destination lane, you need to use drag 'n' drop.
 
 

CW is aware of the issue. So let's hope the bug will get fixed soon.
http://forum.cakewalk.com/Take-Lanes-Clip-cant-be-copypasted-into-a-lane-of-different-T-number-Confirmed-by-CW-m2994675.aspx
 
 
Also, when you use the drag and drop method, do it one by one. Or you will end up like this if the source lane numbers and the destination lane numbers are different.
 

Thanks for these comments.  It's interesting in the clip that Icontakt has posted that there is a mismatch between the track header  which shows the three clips one after another and the take lanes where the three clips are posted on top of each other.  
 
Life for me doesn't seem to be quite as simple as Brundlefly  suggests:  when I drag and drop into an empty lane in a track which has some populated lanes they fragment - even if the source lane is the same number as the destination lane. 
 
If I have data in lanes 1,2,3 & 4 and I want to copy data from another track which is in lane 3 - need to clear lane three.  If I create a new lane (lane 5) and drag the clip from lane 3 to lane 5 then the data in lanes 1,2 and 4 flies away...  
 
Don't many people want to move data between take lanes?  Did Cakewalk think this was something that nobody would ever want to do?
 

richardskeltmusic
Don't many people want to move data between take lanes?  Did Cakewalk think this was something that nobody would ever want to do?

I'd love to. Sadly it's functionality I avoid, take lanes functionality was never fully completed and there are quite a few bugs.