You're experiencing a common off-flavor in cider called THP or tetrahydropyridine. Yes, it's safe to drink, but just doesn't taste all that great. I had this in one of my ciders a few years ago. They say it can taste like toasty, crackers, Cheerios, and I always say: Cheese Nips or Doritos... and at very high levels... urine or "mousy" which is referring to the smell of mouse urine or a mouse den. This can come from contamination from bacteria or wild yeast, or other things stated below. I found additional reference information here:
“Studies show that the set of conditions necessary for mousy off-flavor development include: high pH, exposure to atmospheric oxygen, and, possibly, low concentrations of tannins, pigments and sulfur dioxide."
https://webcache.googleusercontent.com/search?q=cache:VciJe8HXuWAJ:https://www.winebusiness.com/wbm/%3Fgo%3DgetArticle%26dataId%3D48582+&cd=4&hl=en&ct=clnk&gl=us
The flavor tends to age out of sour beers after 2-6 months in the fermenter, kegs, or bottles (although aging periods as long as possibly 8-12 months have been reported...
Many brewers have noticed that pitching rehydrated yeast at packaging reduces the amount/duration of this flavor.
Another reference from someplace:
"In food, tetrahydropyridines are associated with the aroma of baked goods such as white bread, popcorn, and tortillas, and is formed by Maillard reactions during heating. Traditionally, the mousy/Cheerios® flavor from THP is considered an off flavor in both wine and sour beer." Cider obviously should also be included here.
"Brettanomyces produces tetrahydropyridine (THP), which at low levels provide a toasty flavor (at higher levels the perception of THP shifts to urine, or euphemistically "mousy."). I suspect this compound also plays a role in the 'Cheerios' flavors bottle-conditioned sours often temporarily develop.”
https://www.themadfermentationist.com/2015/02/
That should keep folks busy for a while. Keep on Googling.
Cheerio! ;)