This is a bug that exists ever since 1.13, from what I could see. The riptide animation makes the player character spin in the Z Axis all the time. This makes sense during the riptide animation which makes the player character be on a horizontal position instead of vertical like when walking, etc, but does not account for when the player is already in that position, making the player character on a vertical position again, looking upside down and spinning in the Z axis in that position, which in turn breaks the riptide animation. This happens if the player is swim sprinting or elytra flying during a rain, when the player can use riptide.

A suggested fix is disable the tilting that would otherwise put the player character in a horizontal position, if it is sprint swimming or elytra flying. Or, check if the player character is already in a horizontal position to then disable that tilting.