I think there is at least to main factors at the moment.
The primary reason I think is the uncertainty the market is placing on the Magnetite processing ramping up without and problems. On this they should be starting this shortly so we will know soon.
Secondly the issues around Oakajee. This though IMO is a non sequitur, as GBG has stated numerous times that Oakajee is not required until it ramps up to 30 million T/Pa. Karara (GBG JV) facilities support 16Mtpa (Karara Stage 1 and 2) through Geraldton. IMO no valuation is giving yet for expansion through Oakajee. GBG is still doing feasibility studies at the moment on this.
So until the Magnetite processing is in place expect this sort of thing to go on with the share price. Markets hate uncertainty.
Having said that somebody betting against things. ASIC latest shorts report show the following.
57,295,292 shorts from 1,247,487,454 shares or 4.59% of issue shorted. Personally I hope they get burnt.
GBG Price at posting:
31.5¢ Sentiment: LT Buy Disclosure: Held