Assuming it's not the shift coupler.... You can remove the plate on the bottom of the trans an have a look inside. Probably should check before anymore driving.
Look to see if the synchro ring is coming loose. I would do that before dropping. There was a recent thread on this.
While in there check to see if the fork support has not come loose. like this
915 shifting problem
__________________
Gordon
___________________________________
'71 911 Coupe 3,0L
outlawed
#56 PCA Redwood Region, GGR, NASA, Speed SF
Trackrash's Garage :: My Garage