yesterday I carried out several further tests to try to identify which function is responsible for the problem (the drum map or the step sequncer?) .
After these tests that unfortunately made me waste a lot of time, to me it turns out that the function responsible for the problem is the drum map. The drum map that is created using the drum map manager simply doesn't work, the assigned ports and channels are simply ignored in the case of CCs being sent. Using, for example, other tools to check the messages trasmitted it clearly shows that, when using a drum map, CC data are always sent to the "first" saved channel on the drum map even if it is not used and CC are assigned to another channel! Also ports are ignored, not only midi channels, if you have two ports that use the same midi channel (that is correct in the purpouse of create a custom drum kit from several MIDI devices, that can use the same midi channel but are on different ports) the same CC message is transmitted on both even if you want to send it to only one port! and so on...at the end of the matter the functionality is broken.
If you use the step sequencer without creating a drum map, which is not very easy to do because even in this case small bugs (temporarily solvable) pop up when assigning tools and channels, the routing of CC's seems correct. As soon as you create the drum map... disaster!
Of course it's practically useless to use the step sequencer (or drum grid) without a drum map but at least you can understand that the problem is in the drum map and its virtual ports.
What can be done to elevate this problem as bug and so be fixed in the next release? if someone, like kindly User 905133 did, could also do some small tests in order to confirm the bug I think it could be useful in order to elevate the problem to "bug".
Many thanks to all