They won't fix a problem even within the warranty period.
In October 2025, I ordered a GC-03 FNIRSI device directly from the manufacturer. It took a while, but it got there. Now in April, after using it 5 times, it no longer measured radiation. I wrote to the FNIRSI service, they told me to measure the voltage of the tube, it should be between 300-400V. I measured it, took a picture of it for them, it was only 247V. Since then (3 weeks ago), they have not responded to any of the three letters I have written so far, even though I specifically asked for a repair or replacement within the warranty period. I think I will talk everyone out of FNIRSI due to the lack of support...