https://www.ft86club.com/forums/showthread.php?t=125248
This has been an issue since they released this product. I linked a thread above. There is a set screw that is supposed to keep arm and ball secured, but in your case it has either backed out or is stripped.
The other issue with this shifter is the reverse lockout will strike the bolts securing the plate.
FT86 Speed factory should not be selling this product. You are better off getting a refund and buying the STi part.