When launching a boat upwards via a slime block, it will seemingly "bounce" again mid-air upon descent, and break into sticks and planks shortly thereafter.
To reproduce:
Place a sticky piston, facing upwards.
Place a slime block on top.
Place a boat atop the slime block.
Power the sticky piston.
This duplicates MC-108948 (and maybe MC-119369, due to the second part of your sentence).