the blade on my greenworks mower seems wobbly or loose, is that normal?

No. A wobbly blade is dangerous and indicates a failed or loose blade adapter bolt.

1. Remove the battery.
2. Tip the mower correctly (control side up).
3. Use a block of wood to jam the blade so it can't turn.
4. Check the central blade adapter bolt with the correct size wrench. It must be tight.

IF THAT DIDN'T WORK: If the bolt is tight but the blade still wobbles, the blade is bent or the blade adapter/spindle is damaged. Replace the damaged component. Do not operate the mower.

HEADS UP: Always check blade condition and tightness periodically. A loose blade can break and be ejected at high speed.