Messed up light sensor

I'm on my 4th TP now, for hardware defects in the previous ones, and I don't think this one is any different.

Everything is FANTASTIC on it, Feb 22nd build date.

But I've got a major issue with the light sensor...

When it's dark, it reads 0 lumens (yay!), as brightness increases, the lumen count increases nice and smoothly, till it reads around 400 lumens...

After 400 lumens, it skips to 600, then 840, then it jumps back down to 48 lumens... and the brighter it gets after that, the lumen count actually goes DOWN, ending up at 21.

So, if I step outside into sunlight, the light sensor reports 20-30 lumens... so the phone thinks it's dark, and dims the backlight, making it impossible to see my screen.

Anyone else had this issue? I've already hard reset it.