As Janeway ran, she frequently stumbled when the floor went funny.

He frequently stumbles over his new language while ingratiating himself with her and her family.

He stumbled frequently, and his eyes were sore and dry.

Confused, the long-legs frequently stumbled and fell into the deep snow.

He stumbled frequently in the dark and once fell full length in the dirt.

He stumbled frequently, went to his knees a couple of times.

In the course of my wanderings I frequently stumbled across ruins.

He stumbled frequently - went to his knees once.

The ground was littered with scree and, unable to see, she stumbled frequently.

They picked their way through thorn scrub, frequently stumbling in the dark.