Newbie roaster - basic question

Got my Fresh Roast +8 (seemed like a good place to start), SM Monkey.
First roast (7 min+2min cooldown followed by stainles steel colander to
cool bean as quickly as possible)looked oily and dark, went a 30 sec
less on 2d try. Waited 48hrs (in loosely capped Ball jar)
First batch had slightly charcoal taste (gee, kinda like Starbucks), 2d
batch was actually not bad.
(Using Silvia and Rocky, btw)
Anyway, next roast was at 6min+2min cooldown, etc. 48hr wait.
Undrinkable, nasty swill (both batches)
Just to make sure it wasn't Silvia, I brewed a shot of the roast that
John Hornall had done a few days ago. Very, very nice.
Could the 30 sec reduction make this coffee taste THAT bad (really,
really bad..sour, taste lingered for an hour)

Silvia is PID. My dose and tamp are pretty consistent, as is shot
timing.

Any suggestions??

Stan

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