Warp-core+ SHFL on 41CL: strange behaviours

[yann]

Hello everyone! I recently bought a 41CL and I am fascinated by it but I have a little problem: I have installed the Warp-core + rev. K10 MODULE, as per the manual with PLUG WARP B and I would like to use the SHFL command to speed up the operations on the stack but I notice the following strange behaviors:
- as per the manual to enter a numeric digit I have to press SHIFT but I have not found any way to enter the letters identifying the stack levels (XYZTL). Nothing happens when you press one of these letters.
-If I press RADIX I still get nothing (shouldn't I see the prompts populated with the letters of all levels?) But the display quickly turns off and on again.
-If I press '.' (dot) i can see the DATA ERROR on display (this is OK) but I can see "XYZTL" on ALPHA register!
I wrote a little program that puts "TZYXL" in the ALPHA register and executes SHFL: I should get the stack upside down, instead I get the hang of the 41CL!!!
-If I press ALPHA, the command switch from SHFL to R0R4 with the same behavior of SHFL.
On the Warp module I use also LIFO X that works great!
My 41CL is "New" as it has been carefully restored and upgraded to 41CL by The Calculator Store and the keyboard works perfectly.
Did I do something wrong, did I not understand correctly or is there a bug?
A heartfelt thank you for any idea on the matter.