Hi guys

Got a my99
After some hard driving the other day second gear has become tight to select, there's no grinding or anything just a bit difficult going in and out.
Checked the oil and it was low so went down to subaru and topped it up, they said it could be just short of oil or it could need second and third gear replacing. the thing is the problem is only intermitant surly if the gears needed replacing it would do it all the time?
any idea's