problem with control changes assigned to a track

OK i'm french and so desespered that i had to come on this forum. So respect my effort and help me pls!!!!

My config is very simple : an axiom 49 connected in midi IN to the MPC 5000 and a motif rack XS connected in midi OUT.

My problem is simple but it seems that the answer is not quite simple...
when i rec on the track 1 while playing on my axiom and moving the fader on the axiom assigned to CC n°7 (volume), everything is OK. When i play the track, i hear my notes and the volume change with it.
BUT when i rec on the track 2 doing the same (on another channel of course), my CC n°7 disappear on the track 1 (i see that on the step sequencer, no CC written). And even if i push rec without playing on my axiom, the CC is erased.

I read my manual comletely and don't find the answer. I'm tired with this translation too. If you can help me, ca serait sympa!!! thx

Why dont you use the sliders on the MPC itself to automate volume?

OK i listened to you and i tried to use the faders on the mpc.

here it is:
i created 2 programs with qlink assignations for 2 faders (CC 7 (volume) and CC 22).
I recorded on track 1 (midi 1A and program 1) moving the 2 faders and i recorded on track 2 (midi 2A and program 2) doing the same.

Then in the step edit, CC 22 is written on the 2 tracks but CC 7 is written only on track 2.

My MPC is mad, right??