Do you see vertical streaking in autoradiographic images only or in CBB (Coomassie Brilliant Blue)-stained gels as well?

If vertical streaking is accounted for by sample precipitation related to protein solubility, samples may be centrifuged just before loading, or the concentration of separating gel may be decreased.

If vertical streaking is accounted for by sample overload in terms of large quantity of the whole protein samples or highly abundant proteins, samples may be diluted or voltage may be lowered.

You may have overloading, but I also would be concerned about protein degradation, which will produce streaking.

As suggested above this could be happened due to protein degradation which happens as a result of high voltage or low conc protease inhibitors.