In the Saiyan Saga, before Nappa and Vegeta are due to arrive, the heroes gather the Dragon Balls and summon Shenron in order to revive Goku. However, before they can, Oolong asks Shenron if it would be possible for Shenron to defeat the Saiyans instead.
Shenron, however, states that it's not possible; clarifying that he cannot affect anyone more powerful than Kami - his creator - against their will.
So, we know that Shenron couldn't use his power to affect Nappa and Vegeta directly as they're more powerful than Kami.
However, what about their Saiyan Pods? Could he instead have caused those (as well as Vegeta and Nappa's scouters) to malfunction - either drastically slowing down Nappa and Vegeta's arrival to Earth or outright leaving them stranded in the vacuum of space with no means to call for help and with their pod's life-support system comprised or failing entirely?
(Admittedly a pretty morbid way to go, but it would end the threat at least).
Do you think Shenron could have done this, or would he be unable to and the original wish of reviving Goku would be used?
Curious to see what you guys think.