HI Totalnoob
Yes, that was my first gun also, got it from my dad when he got a new one, it probably shot more fish than most of us!
It is a very old Arbalete grip, I don't use mine anymore, it started to go off at random. not that big of a problem for me, but nobody wanted to dive with me anymore!
My advise is to take it to Louis or Riaan, let them have a look at it.
THE LAST THING YOU WANT IS A SPEARGUN THAT YOU CANNOT TRUST!
Hope it put fresh fish on the grill!