Brown residue inside still and off smell in water run

[LocalRepeater]

Hello, not sure if this is the correct place for this post so sorry in advance.

I've built a reflux still out of copper and following advice on the forum did a vinegar run with a 50/50 mix of vinegar and water. After doing this I cleaned out the still and there seem to be a lot of brown residue inside the reflux column.

I cleaned as much of the residue out as possible with a stainless steel scrub for at least 20 minutes in hot soapy water, but even after this when I run my finger around the inside of the reflux column my finger would discolour slightly and the inside of the column was still not totally shiny.

I then tried a water run hoping it would clean out some of the residue. The water came out completely clear but had a sweet vinegary smell to it.

Any ideas what caused the brown residue to appear and my best bet for getting rid of it? or what is cause of the smell in the distilled water?