Help: SR5 '99 pickup routing (3 way switch)

I’m new to the Ernie Ball forum, but I came here in search for help, if possible…

Sorry for the long story that follows…

I’m from Portugal and a proud owner of a Stingray 5 with the serial # E08770 that I believe was made in 1999, I own it since 2002.

It’s been my main bass since then with no big issues, but the last rehearsal I noticed that the bridge position of the 3 way switch was way louder than the others, to the point of creating feedback. The other two were with significantly lower volume than usual.

I haven’t done nothing to it, it just happened. I took it to a local tech to help me with the issue and I said to him what each of the positions were: parallel (bridge position) / single coil (middle) / series (neck). He said he will see it and when I went there later to pick the bass he said to me that it was nothing like that, it was bridge position – humbucker; middle – bridge single coil; neck position – neck single coil; and that it was normal that the bridge position is louder because of it being a humbucker… I doubted it but said nothing, didn’t want to argue of something I wasn’t sure.

I remember that there were no volume differences between the three positions, only EQ differences, right? This way I can only play in one of the positions because of the volume differences, and I used to change it for some songs without any volume issues. Strange…

I’m tempted to take it to another tech, in a store in Lisbon that are more experienced with basses but I’m not sure if he can do anything to put it like before… What could’ve happened, anyone knows?

I also would like to ask if anyone has the schematics of Stingray 5 from this era, 1999, maybe I could bring it to the tech to help him in seeing what’s wrong with the bass…

Can anyone here help?

Thanks