The story of which you are thinking sounds like Kenneth Bulmer's Behold the Stars (1965), which was previously asked about and successfully answered here.
The protagonist does use a kind of teleport gate to service ummanned sublight "carrier" spacecraft:
A fraction of a second before he had been standing on concrete, deep
within the Earth, surrounded by armor and machines and men and women;
now he stood in the hollow steel hull of a spaceship spearing through
space fifty light years or more from Earth.
That meant little; it was his condition of work.
He set about servicing the carrier with methodical thoroughness,
forcing himself to slow down, to make a good job of it.
No damn Gershmi would make him skimp a job.
The fuel bins were nearly empty. He'd do those first, as per schedule.
At the start of the story, some maintenance men had not been coming back, as you recall:
"Say, Dave, have you heard? Jimmy Kinross went missing on his last
Ward put the coffee cup down deliberately. His mind blanked for an
instant, then he said: "No, Bill. I hadn't heard. That's bad."
"Well, what's all this nonsense about a miss?"
Roscoe rubbed a hand across his forehead. "We just don't know, Dave.
He's just disappeared. We've got to look for any eventuality however
"Well what do you think happened?"
Roscoe looked uncomfortable.
"Jimmy was servicing a carrier on the Ganges run."
There is an orbital battle against the antagonistic Gershmi towards the end, in which a carrier ship is used as the "beachhead" for the invasion:
The speaker coughed and a crisp voice said: "Hear this. This is
Admiral Hawkins. You men are about to gather in the harvest sown by
men long ago. We are about to claim a solar system for Solterra."
Angrily he shook himself. He had to clear his mind. He had to
concentrate on his work in this vast and intricate job of assembly.
One weak link in that chain and decades of devoted work would be
The far door opened and eager hands reached in and hauled him out. A
voice on the headphones shouted: "Keep it moving there! Come on,
soldier, get your tail outta that box!"
All about them in space, tethered by snaking tie lines, other men were
assembling boxes, Marines were fanning out, Navy techs were already
assembling the parts of a picket boat; all this area of space swarmed
The beachhead is threatened when it is discovered that the Gershmi are already at the destination:
"Hurry it up, Box Nine!" The voice hammered in Ward's headphones.
Box Nine. That was Ward and Nkomo. Their box was a high density one,
capable of transitting heavy beams, nuclear-drive components, venturi
tubes, all the big stuff necessary for the construction of a spaceship
in space. Box nine was wanted in a hurry.
The spaceship now lay broken down into components on some distant
planet of the Solterran Federation -- Mars was a favorite location. As
soon as box nine was functioning that spaceship could be beamed over
two hundred light years. Ward and Nkomo sweated at it as they made
that scientific miracle possible.
A voice, a harsh, choked voice, full of horrible disappointment,
shouted in his ears. "Red alert! Bogey showing around the planet's
limb! Declination four-two-thirty! Headed this way!"
A spaceship -- here!
The voice again, grating, demanding. "Bogey now identified. Gershmi
light cruiser! On collision course!"
The part with the booth on a planet surface is a key part of the story:
He stepped out the far door, adjusting his body to the anticipated
near free-fall conditions in the carrier and fell full length on his
face, his body crushed down by a stunning and unexpected and
altogether terrifying acceleration.
The breath had been thumped out of his lungs by the drop. He shoved up
on hands and knees against the force dragging him down, feeling the
blood pounding crazily behind his eyes, the drag on his muscles, the
loosely sagging feel of his stomach muscles. Then all idea that
acceleration was clawing at him was dispelled.
He was kneeling on a muddy ground, on earth and clay and a short squat
mossy growth blotching that ground, and around his as he slowly
rotated his head to look, dragging against that inexorable force, he
saw squat scaled trees and dripping branches and dangling fronds of
metallic creepers, and in his ears from his outside pickups the sound
of dripping water and sloshing mud and the insane chirruping of some
unseen animal life mocked him.
He was on planet!
... though it is quickly explained that the "box" was more likely placed on the surface by the enemy than that it had survived a crash:
How had the box come here?
The first and obvious answer lay in what Lazenby had been saying: the
carrier had been trapped by the gravitational pull of a small red star
and had fallen onto the surface of a planet. But that was absurd. Even
if the carrier had not been traveling at something like point four of
c, even if it had just fallen onto the planet from a simple orbit, it
would have been vaporized, smashed, utterly destroyed.
The boxes were built ruggedly; but even their armor couldn't stand up
to that type of punishment.
So -- the box had been brought here.
The planet is not Venus, but "the Venie war" is mentioned in the scene.
The cover of an edition published by Bridbooks in Israel matches your description: