Mysterious Extra Data in Channels (Bug?)

[Really Weird Person]

I wonder something? For some reason, if you do Copy Pattern (by right clicking a pattern number at the top, then clicking on Copy Pattern), some mysterious notes are placed in the channel after the last one in the song. For example, I have a song that is 18, channels. I am mixing it with another song. For some reason, if I do a Copy Pattern, some notes get placed in Channel 19 that I do not want. However, if I do Control-5, copy the pattern) (Control-Insert) (or C, I use Insert now), then paste (Shift-Insert or Control-V) (I use Shift-Insert now) it into the the other song, I do not get those extra notes in Channel 19.
I changed the Copy and Paste combinations for three main reasons.
1. The Insert key is much closer to the arrow keys than C and V.
2. Control-Shift-Insert does not do anything, so I only have two options (either copy or paste).
3. I often got frustrated because I would want to paste something, but I would bump C by accident and copy nothingness! I figured that I might not do that as often with Insert.

[LPChip]

It almost sounds like these keys also trigger something else.

[Saga Musix]

I think i experienced something like that years ago in the old modplug. i found out that those notes were notes from the 1st channel...