was this maybe an issue with the cd-writer? maybe at the speeds it was writing with?

I mean maybe, we had a few different models we burned with, but only a few. With the volume we needed to burn, we needed the speed. But, as a counter-point, I will say that with Taiyo Yuden discs our failures were very low, so the drives were only a component. IIRC we were using a lot of LiteOn drives which at the time were not bad.