They can design the Voyager probe to function well in very cold temps ...
Not in the 1970s they couldn't, and they also couldn't produce technology required to got to the moon in the 1960s either ... so the faked the moon landing. Just remember what kinds of junk cars people were driving in the 1960s and 1970s.
I worked at NASA and often participated in radiation/temperature testing of electronic components, and even with today's technology, 90% of the tech they claimed was resistant to radiation and extreme temperatures failed the tests miserably, and this was in the early 2000s, not in the 1970s.
And this is to say nothing of the fact that it's the height of absurdity to pretend that Voyager can beam meaningful signals back to earth using a 23 watt radio ... from allegedly 24 billion miles away. That signal would be so dispersed over those distances that it could not contain any meaningful data (similar to the absurd claim that Webb is beaming high-definition data from a million miles away). In real practice, the higher bandwidth you get, the more concentrated the signal has to be and the more power you need to send it. If we could beam high definition data across millions of miles, cell phone companies would have gotten rid of the cell towers they have to build every mile or two a LONG time ago, to say nothing of the absurdity of hitting the target with a high bandwidth signal from a million miles that would be so tiny as to be imperceptible ... WHILE the earth is allegedly rotating at (an average of) 700 MPH AND revolving around the sun at over 6,000 MPH. You'd be a great shot if you could hit something the size of a jar lid from 100 yards away. Now move it to a mile away, and then to 1,000 miles ... and you're not even close to the proportions we're talking about from million miles away. And now put the target into motion at 6,000 MPH.
You recently had a company set a record for high-bandwidth transmission at about 230 miles (across the Mediterranean), and they had to use line of sight microwave signals, since you need a very concentrated (and therefore line of sight) beam to carry high-bandwidth data. Now try to send high-bandwidth data over a MILLION miles. To get high bandwith, you need a concentrated, tight, and therefore line of sight signal ... and I'm sure we're getting that from Webb at about a million miles away, as the earth rotates 700MPH and flies around the sun at 6000MPH. Suuure. Of course, on a side note, at 230 miles (with the aforementioned microwave signal across the Mediterrean), it couldn't have been line of sight on a globe, since the target (150 foot towers) would have been obscured by 8 miles of curvature bulge.
Back in the day when we hard our rabbit-ear antennas, and then even the small dishes, to get a decent TV signal from most stations, you had to point the in just the right direction and just at the right angle to have some stations come in ... and that's when the transmitters were about 20 miles away, much less 24 billion.