When you use the channel manager to reorder channels, you virtually move those channels around in the song.
If you have different channel volumes per channel, and you reorder those, the current state of those channels is being kept, untill you play the song from start.
Lets say:
before you order the channels:
Channel 1 has 64 volume
Channel 2 has 64 volume
Channel 3 has 10 volume
Channel 4 has 30 volume
You play the song and at this moment it sounds correct.
Now you reorder Channel 4 to be before channel 2.
So:
Channel 1 was 64, now is 64.
Channel 2 was 64, now is 30.
Channel 3 was 10, now is 64.
Channel 4 was 30, now is 10.
This behavor is expected, but, until you replay the song from start, what is supposed to be 30 volume is played at 64 which is way too loud. What is supposed to be playing at 64 is being played at 10 which is almost silent, etc...
A fix would be to trigger a volume initialise during the channel reordering process.
EDIT: even worse... Untill the song is restarted, changing the volume for the old channel will result in changing the sound on the new

So If i change the volume of channel 3 (10), the content of channel 4 changes of sound.