I have just recieved a used explorer 2 and the upper shaft is very loose and wobbles and even fell out after about ten minutes detecting. Wanting to change the whole shaft with another type! Has anyone tried this?
Check the red rubber piece under the lever. There should be a metal plate between the lever and the red rubber. These are glued to the rubber and sometimes fall out.
If so, you could make a new plate or call Minelab for a replacement.
The EXP II can be put together upside down. It is easy to do if you take it apart to clean as you should occasionally. The bottom section will go in either way to the upper section and the upper section is curved making it longer one way than the other, this longer side goes to the locking lever side. What happened sounds just like what I did, including the shaft falling out. A quick inspection told me it was backwards.