DALI addressing error

I encountered problems with addressing DALI lights. I have an installation with 9 lamps and I want to address all of them with the function block called "fb_DL_RNDAddr". It almost finishes but only addresses 0..7, and nothing on 8. Only one lamp that cannot be addressed. We tried to replace the lamp, and still nothing. Also tried with connecting that only one lamp directly to the C-DL-0012S module and still nothing. I readdressed automatically all of the lamps and still misses the 9th one.

What would cause this problem and how it can be solved?