Yes, this is a kind of annoying part in anime. Mostly, it only make the show look terrible.
It might caused by the following reasons :
- Animator shortage.
- Supervisor's nonfeasance.
- Low budget.
- Production dead line's near.
- Outsourcing's result.
It mostly be bad for anime ; but some are not.
Take Konosuba as example, it really has relatively high amount of QUALIT " IES ", yet it perfectly match its jolly plot. So this opposite effect might considered as a huge success :)
So as Gintama, when Korean outsourcing QUALITY take place, it even regarded as official prank :/ .