Exclusive for a dub of a show, but the original DiC production of Sailor Moon ended up suffering a loss of quality rather rapidly with even the original English dub's voice actors outright stating that they agreed with fans that the dub was completely rubbish. In fact, the show's second voice actress for Setsuna/Trisha/Sailor Pluto, Susan Aceron, even said that it was a mistake that she was cast to be in that series at all.

There's actually a known and stated reason for this, however, as given by Roland Parliament who was the voice of Umino/Melvin and the show's second ADR (Automated Dialogue Replacement) director in his autobiography Sailor Moon Reflections.

In short, the first voice of Sailor Moon, Tracey Moore, was also the show's first ADR director but was so heavily overworked that she suffered from burnout and quit thirteen episodes into the show's production (episodes 1-11, 15 and 21), so when she quit she was replaced with Roland.

They tried to keep her in the role by replacing her as ADR director with castmates who had smaller roles in the show. But because of clashes with a producer at Optimum Productions, Nicole Thuault who also heavily clashed with Moore while she was the ADR director, Parliament was fired from the role as ADR director as well as his replacement John Stocker, who played Rei's grandfather in the dub.

When Optimum completed their original recording sessions for the show, DiC decided to stop licensing the show and left them stranded. But Cartoon Network and YTV wanted more episodes dubbed so they paid for it themselves and ordered the adaptations directly. All 77 remaining episodes... in four months. Optimum couldn't get most of the original cast for a number of reasons - some of the voice actors hated the conditions and refused to come back while at least one of them outright couldn't due to being on maternity leave.

After this, Thuault decided that she might as well take on the role as the show's ADR director instead. This was despite the fact that despite being a producer on the show's English dub, she didn't fucking speak English and in fact needed a translator on-site to help her communicate with the cast and crew. By the way, did I mention that Optimum was based out of Ontario?

So, the ADR director wasn't able to properly quality control the recording, they had to adapt 77 episodes of the show in four months and most of the original cast was gone. They only had four hours to record each episode and took were only allowed to do two takes for each scene/episode and decided to use the one that wasn't shit. Quality dropped immensely, the seasons adapted were widely hated until the entire series was re-dubbed by Viz and it proved to be such an old shame that the DiC dub will never be rereleased again.

And for added hilarity, when they were doing the translation of the scripts into English, because of a stupid term of the contract that they were using, they weren't adapting the original Japanese scripts of the show but the earlier French dub produced in Paris.

Oh, and here's something funny I wanted to bring up as well. They had to make some changes to the show to appease US censors, mainly because the show could actually get somewhat violent for US audiences. One pair of junior high school students were expressly a pair of lesbians in the original Japanese version which was turned into them being cousins in the English dub... but they didn't fully remove all of the pretext, so it made them look like teenage incestuous lesbians instead.