A series can look extraordinary in one episode and noticeably weaker in the next. The variation comes from how episodes are distributed across teams and how little slack the schedule contains.
Episodes are made in parallel, not in sequence
A weekly series cannot be produced one episode at a time, because a single episode takes several months to complete and the broadcast gap is seven days.
Several episodes are therefore in production simultaneously, each with its own episode director, animation director and largely separate group of key animators.
Differences between those teams show up directly on screen, since each brings its own emphasis, its own sense of timing and its own solutions to the same character designs.
Work is distributed unevenly on purpose
Productions concentrate their strongest resources on the episodes that matter most, typically the opening, the climax of an arc and the finale of the run.
Connecting episodes receive proportionally less, which is a deliberate allocation of a fixed total capacity rather than a failure by the people making them.
Viewers notice the contrast most when a highly resourced episode is followed immediately by a conservative one.
Outsourcing spreads the work further
Studios routinely subcontract whole episodes or individual sequences to other companies, sometimes in other countries.
Those partners work from the same designs and instructions, but interpretation varies and supervision at a distance is harder.
The correction pass exists to bring everything back toward a consistent standard, and it is the first thing compressed when time runs short.
Schedules leave no room for recovery
Broadcast dates are fixed in advance, and an episode delayed at any stage compresses everything downstream rather than moving the deadline.
The final stages, where inconsistencies are normally caught and fixed, are therefore the ones that lose time when anything goes wrong earlier.
Series occasionally pause broadcast for a week precisely to recover this margin, which is now understood by audiences as a signal about the schedule.
Consistency and peaks are a trade
Some productions distribute resources evenly and deliver a uniform standard throughout without exceptional moments.
Others accept variation in order to make particular sequences remarkable, which is what produces the individual episodes audiences remember for years.
Neither approach is straightforwardly better, and the choice is usually made by the series director early on, long before any of it is visible.