Welcome to the Wonderful World of Chinchillas!
Yes, your little one has been orphaned to many times already. I try to make sure none of mine have more than two homes ... mine and their new human parents ... it is very hard for them to adjust. Chins do not like change.
There is something that has changed that they are not happy about. Chins rarely change that drastically without reason. Are there any warning signs before biting? Like trying to run away, hiding, fussing at you, trying to push your hand away, spraying you or a firm nip not breaking the skin? These are all "warnings" a chin will give you before they take a bite that will draw blood.
CAUTION: ALWAYS wash your hands and face before handling your chin ... their eyesite is not that good, but their noses are! They may smell something on your hands that smells "tasty" to them ... they may think the smell is a treat and want to taste it.
Be very careful and take note of anything that happens just before and at the time the little one bites you ... you need to find the common denominator and eliminate it. Food on your breath, a particular outfit, change in washing machine detergent or softener, noises around you. TV or radio program with the same or similar sounds. Tossing something near the cage (like clothing or an object), this can startle them. Strangers to the chin. New deodorant or perfume? Sometimes it can be the simplest of things you would normally think would not bother an animal or chin ... but can do so. Just the scent of the cats may upset them ... there may have been a cat or dog in one of the previous homes that terrorized them.
Jo Ann