Spark ST-150CW problem

I have a Spark ST5-150CW headlamp for some time. Recently it started to behave strangely.
I am no longer able to switch modes. The light is stuck in one mode, which seems to be lower than Fenix E01 (annoyingly low). The battery is immedion 2400mAh, freshly charged – the charger shows 1.27V.
Is there anything I could try to return the flashlight to its former functionality, or does it look like it is irreversibly broken…

Thanks for any advices

try another battery

I did, I have 3 another imedions, 2 GPs :frowning: (Should have written this in my original post)
I am too cheap to buy some lithium AAs, but no NiMhs I have at home made any difference.

Could it be that I somehow destroyed the electronics - is there any way to test it? (I have only used NiMhs)