buon giorno :welcome:
dont worry about your english, we can understand you and that's good enough for me
look on this forum as a way to practice your english, i'd love to learn Italian too.
anyway, i have the Nitecore EX10 GDP and its working fine, i abused it and broke the lens but no big deal there, apart from that, everything works great.
I tried using my Trustfire protected 16340 but its too long, roughly 34mm as compared to my Soshine unprotected 16340 which is roughly 2mm shorter. that slight difference is enough so that my PD will not work when i use the Trustfire, i can have it either permanently on or use it in momentary mode.
As for the runtime, i have used my EX10 for 20 plus minutes at maximum output with no problems, have not tried it for any longer just yet. I think there may be something wrong with your D10 as the batteries seem to be working fine in your other lights.
Send an email to the seller you got it from, if all else fails, contact nitecore directly, that is what i did when i broke my lens and they are shipping one to me for free (or so they say
)
Good luck with your light.