I would say that this is a sensor issue because sensor is read line by line.
If NEF files are losslessly compressed (this may be switched off IIRC) card corruption will not cause these simple artifacts and will rather cause box artifacts or whole image corruption.
The ADC converter is a bottleneck which gets all the throughput. There are not much more than two unreliable places - the ADC and the flash card, everything else is very complicated and would produce more more complicated errors (RAM is another place which can fail but it is usually broken in non-moving places). If NEF compression is turned on flash card failure cannot produce linear artefacts because compression is usually done in tiles. Therefore, the problem lies in ADC.