Fall damage on stairs

Taking fall damage walking down stairs (even while crouched going extremely slow) and dying up to a minute after i have reached the bottom of the stairs.

the last time this happened all of the items i was carrying were not there when i returned to the spot (and i almost died again going down the stairs again)

This has been a problem for several days now and there is also tons of lag. when my wife is logged in as well we are jumping around on eachothers screens.