Ignoramus30421 wrote:

I think that my other problem is a 10+ year old paste flux. Could it be?

Probably not, assuming it still has the same "paste" consistency as it's
always had. Even if it'd dried out to crust and lumps, it should melt in
use; you could try dissolving the crust and lumps in alcohol. I'm pretty
sure that rosin continues to be rosin, unless it gets moldy or something.

Hope This Helps!
Rich