martinr In the TS runtime, when setting a mix pair the key used is from.name + to.name This can create a potential conflict, e.g. if one animation pair is named 'ab' and 'c' and another pair is named 'a' and 'bc'. In both cases, the key will be 'abc'.
Mario Good catch, thanks for reporting! Opened an issue here [ts] Keys for animation mixing data may be ambiguous · #1065