For a resilient object (actor muɴ-, -um- & theme) to spring up and down, from the center or ends, as a bridge, a floor, a carrying pole, and the like.
Munyobod han langtay an enengwāmi ti nadūnut.
The bridge sprang up and down as we passed because it is rotten.
For someone (actor CVCV- + -um-) to spring a resilient object (theme i-) up and down, from the center or ends, as a bridge, a floor, a carrying pole, etc.
Adī'a yumoboyobod hinan langtay.
Don't always be springing the bridge up and down.