Old fets was to slow for switching application , if i would ordering from farnell i would try some fets with different specs. But probably with faster fet flashlight modes will be brighter
Update: I received the FET thefreeman suggested and replaced it on the 2nd driver. Success. I have a fully working torch! Thank you thefreeman.
I will replace the FET on the 1st driver and see if it helps with that one too.
Nice 
The 1st driver is fixed too! It was just the FET here too, only it was the gate that was sorted to the drain in this one and was causing the strange behaviour. Thanks to the freeman, I have 2 fully working expensive and rare torches. Thank you!
thefreeman, out of curiosity, I noticed that the FET you suggested (the FET I receiveved from Farnell) has a different code on it. I guess you probably improved upon the original or it is a replacement for a part no longer in production?
It’s different than the original (AO4409) yes, firstly they don’t sell the AO4409 anywhere except Chinese sources, but also I chose one with better characteristics.
That’s great.
Is there a noticeable practical difference, such as higher output due to less internal resistance or anything else?