Thanks for the answer, I already have the latest firmware from the ASUS website...
The BD-R I used was actually a Mediarange 50Gb (french amazon link), I know they display "VERBAT-IMf-000" in Imgburn but I'm not sure if they really are the same. But I also have some real Verbatim 25Gb/50Gb (Real package + VERBAT-IMf-000) and they go through the same type of invalid CDB errors.
This is already the second drive that I try on this computer, at first I bought a slim laptop BD burner and an external USB case and I had a really rough time to complete any BD burn, high fail rate with a lot of I/O write error / CDB errors.
I then read on this forum that slim drive + USB are crap so I told myself OK let's not play it cheap, I sent the slim drive back and bought the Asus BW-16D1H-U PRO USB (link). With this one I managed to write a BD-R daily without a problem for a week, miracle! Except that it didn't last CDB errors came back, only less often than with the previous burner. I kept burning BD-R for the past 2 month with the occasional inexplicable CBD error (super frustrating of course). I tried some tricks I read here and there : change write mode to Incremental instead of SAO / add "perform OPC Before Write" option / reduce burn speed / Close Windows Defender anti-virus during a burn... -> I doubt any of those had influence on the problem. Since I got the ASUS I successfully burned 41 BD-R and failed 15.
I also read a lot on forums that USB is unreliable for burners so I thought the problem might come from that. 2 days ago while cleaning my PC tower I discovered 2 unused SATA port on my motherboard, hidden behind my graphic card... the only reason I went for a USB burner in the first place is because I believed there was no more free SATA port on the mb... Yes I am a gigantic fool Anyway I decided to extract the ASUS BW-16D1H-U drive from its USB case and put it directly in the tower connected with a SATA cable. Went OK and I burned a BD-R perfectly afterward. I hoped it was the end of it but NOPE, next burn was the failure in my first post...
Are you sure that the problem will go away if I change the burner again? As you can imagine my little Bluray burning adventure is starting to cost me a lot more €€€ than anticipated
If the answer is yes do you have any recommendation for brands / models?