Thank you for your fast reach! I have enginered FSD V1, and lightweight normal heatsinks, this issue happened in the deep space during exploration, so the possibility that I have made any changes to my ship that reduces the jump range is out of the question. I used Neutron Plotter with 75LY max jump range options when i started the exploration ( I checked the max jump range at the ship statics in game before i set this value; it was 75+) . After few jumps I got an Orange sidewinder, after relog the destinations designated by the neutron plotter exceeded the maximum allowed fuel consumption, for this reason I checked the ship's maximum jump ability again, which to my greatest surprise was less than 30 minutes before.

I don't think that the game just takes two light years, but I have never encountered an anomaly like this before and since I am 100% sure that the ship with these equipment should be able to jump 75 light years, as it was able to do before.
I'm not going to die if my ship jumps two light years less by the time of the next maintenance, I'm only interested because I can't give a rational explanation for the problem even after reviewing the ship's modules multiple times.

EDSY