Unfixed, unstable, unsteady, wobbly, weak...
Unreliable is another word for unstable. Additional synonyms include unsafe, weak, changeable and wobbly.
Thomas and Friends Wobbly Wheels and Whistles - 2011 V is rated/received certificates of: UK:U
The wobbly wagon wheels squeaked incessantly.
wobbly like crazy
"It was/has been wobbly."
make it wobbly
The fawn was a bit wobbly on her feet, at first.
A cheese souffle is pretty wobbly!