I'm presuming you mean escalator, in which case they don't require movement to decrease the risk of collapse.
They potentially can only collapse if the rail they rest on or the linkages between steps break apart. Technically very highly unlikely, as they're designed and engineered to carry much more weight than they need to, even when stopped. Lots of fail safes built into them.
The only danger is the assumption that they can be used as stairs when stopped, as the stairs are not designed to the same dimensions as regular stairs so people could fall or trip if not careful.
