During the USS Voyager's return to Earth, the ships lost around 15 shuttles. It was never explained or shown to us in the show how the Voyager crew were able to constantly create new shuttles despite being a medium sized ship thousands of lightyears from Federation space. It can be assumed that the crew replicated shuttle parts and constructed a new shuttle once one had been destroyed. This is one aspect of Star Trek: Voyager which has attracted a lot of negative attention many from fans who feel it was unrealistic for crew to be able to constantly replace shuttles/construct warp drives in their situation.
Throughout Voyager's seven year journey, the crew count appears to go up and down several times without any apparent reason why. In season 2 episode 1 "The 37s", it is mentioned there are 152 crew members on board. In season 3 episode 2 "Distant Origin", alien sensors pick up 147 lifesigns. In season 5 episode 4 "In the Flesh", the Doctor implies there are 127 crew members. In season 5 episode 13 "Gravity", it is said there are 152 crew members. In season 5 episode 15 "Dark Frontier", there are 143 lifesigns detected on Voyager. In season 5 episode 22 "Someone to Watch Over Me", there are 146 crew members. In season 7 episode 20 "Author, Author", there are still 146 crew members despite there being several deaths since the events of "Someone to Watch Over Me".Over the years, we saw that Voyager lost approximately 33 crew members. However this was not reflected in the crew counts we heard throughout the show, and an inshow explanation for how the crew numbers jumped up and down so much seems impossible as besides Kes, Neelix, Naomi, Seven and Icheb and the 5 Equinox crewmembers added in Season 6 Episode 1 "Equinox Part 2", there were no permanent new additions to the crew throughout the show. It is far more likely that the writers simply did not keep tabs on the number of crewmembers. This is also reflected in other ways such as the surprise sighting of a female Vulcan on board Voyager in season 7 episode 4 "Repression" which directly contradicts the events of Season 3 episode "Blood Fever" and Season 5 episode "Counterpoint". Yet in the Season 3 episode "Flashback" Tuvok does clearly mention there are indeed other Vulcan crew members aboard Voyager. Due to the nature of the shows premise being that the ship is small and far away from Federation space, such continuity errors are particularly jarring.