Interesting. Are you running different systems? If so, can you explain which (and which desktop environments) so we can (try to) reproduce?
Yes, the one was on Void Linux (no desktop environment), the other on Kubuntu (KDE).
It's probably worth a bug report to the TBB team so that they can investigate why fingerprints would be different. Having a unique fingerprint across instances is the very goal of TBB.