K3B: Fails verify when burning Bluray DL discs

At first I thought my internal BD-R burner was at fault, but this happens with a USB 3 burner, too. The disks burn, but usually fail verify. However, if I do this, it doesn’t report any error:

cmp /dev/sr1 /home/user/tmp/Alice.iso

And the disks *seem *to have valid data, as far as I can tell. Single layer Bluray disks verify, though. I couldn’t find any current threads on this subject…
Is this a known problem with K3B, or cdrecord? I was going to try burning with growisofs, but that was burning at only 2.4x, I didn’t want to wait all night for it to finish.

I have another USB Bluray burner, Pioneer BDR-XS06, I just burned a BD-R / DL (50GB) disc, and it verified. I’ll have to use this one in the future to see if it fails to verify. I’m not really sure yet if it’s K3B or the other 2 drives that aren’t cooperating. Too bad the Pioneer is slower than the other two, it usually burns slower than what disks are rated for.

Forgot to mention, single layer 25GB M-DISCs work ok. 50GB and 100GB M-DISC and “regular” BD discs usually fail verify. So now I just create the ISO image first using K3B (because one time the image got removed when it failed to verify with K3B, so this is “just in case”), then I burn the ISO image with K3B without verifying, then I use

cmp /dev/sr1 /home/user/tmp/image.iso

to verify. This save lots of time having to re-verify when K3B fails to verify. So far, 25GB discs work fine the “old” way, so I let K3B do everything.