The drive may not be rated at the high speed in combination with the media used. If you realise that a lot of cheap media are turned out in factories where economy wins over quality, you might have DVDs where the manufacturer ID might be fake and this causes the writer to choose the wrong burn power, which become a more serious problem at high speeds.
The drive might require the latest revision of firmware to work at high speeds. Something like this: Maybe when the drive was first issued, it was rated at 8x for all known DVDs and at 16x for QualityRUS DVDs and other brands were not available yet. As more media brands came out, the drive manufacturer might have updated the firmware to handle those. But you haven't got the latest firmware. BTW this also applies to PVR appliances.
And cheap media are just that, cheap. They are ok for handing your relative copies of programs you recorded off free-to-air TV, but don't expect them to keep data for more than months or a year. I have seen media where it was obvious that exposure to air had caused the dye layer to thin and start developing pinholes.
Having said that, I don't believe it is necessary to go down to 1x. I hardly ever have problems with 4x.
You have to watch k3b. It could pick a high speed when you choose Auto, but this is not compatible with your drive or medium for reasons given above. So set k3b manually to use 4x or less.
BTW if you want to make archival quality DVDs, two words: Taiyo Yuden. The real ones, made in Japan. And good storage conditions of course.