Hello folks,
You know what: it was a crazy story
I've received the replacement motor (E166361):
-Size is the same
-except the plastic part surrounding the axle is 5mm in diameter while the motor cradle is 4mm
-As it is plastic, I can file it, but it's boring...
...
And I did a test with the motor on the bench (not inside the loco)... and guess what : nothing with loksound 5
At this stage of investigations, I was thinking my old Windows XP Virtual Machine wasn't able to drive the loksound 5 (the last possible version is 5.1.10), even if the decoder tester was absolutely fine with the Loksound 5 ???
...
I've set a new Virtual Machine with Windows 10, reinstalled the lokprogrammer v5.2.2... same nothingness
...
I've decided to pick a Lokpilot 4 (no sound) I had in stock, setup some basic programming... and miracle it was running all times

.
...
At this stage, the status was:
-All OK with lokpilot 4 (no sound): PCB, motor and lights, either with version 5.1.10 or 5.2.2 of the lokprogrammer software
-OK 4 times over 10 with lokpilot 5 (no sound): PCB, motor and lights, either with version 5.1.10 or 5.2.2 of the lokprogrammer software
-Always
KO with loksound 5: PCB, motor and lights, either with version 5.1.10 or 5.2.2 of the lokprogrammer software
-All 3 decoders OK with decoder tester 53900
Crazy, isn't it ?
So what is remaining:
-The loudspeaker of the loco ? maybe some short ?
-The PCB itself is OK, because it runs with LP4
-The motor of the snow plow is different from the motor on the decoder tester, but again, the motor of the snow plow works fine with LP4
...very few other alternatives
And finally, by re-reading the specs of the various decoders, could that be a power draw issue ?
The power block I use to power the lokprogrammer is 12V, 500mA... Mmmh, not a lot !

In the past, when I was testing some smoke devices with the lokprogrammer, it had frequently power cut off because of too much power drawn.
And, after digging in the stock, I found a 12V, 2.5A power block for LED ribbon- with the right plug...
...Drum roll...
YES, that was it 
. Loksound 5 is now fine with the PCB
All that mess because of a not enough powerful power block

!
In summary, the original motor is fine, the new one is also fine but with an issue to insert it, the PCB is fine and the Ledbar too...
Now, I'm going to rewire all in the snow plow, put some additional LEDs, and set it definitely.
Next post to come: A video with all stuff running (I hope).
Cheers
Fabrice