One potential thing that might be happening, although I don’t know, is that you’re running into an analog vs digital design difference. A voltage into Mangrove’s pitch input literally controls a circuit that pitches the Mangrove’s output, but a voltage into Just Friends’ time input is run through an analog-to-digital converter, and then affecting the computation that way.
This digital implementation usually means there’s some clipping of the allowable voltages into the input, so what I suspect is this: transposing up 5 octaves (which is… a lot of octaves) means adding 5 volts to the pitch CV. This might cause some of the note voltages you’re outputting from O_c to exceed the maximum allowed input into Just Friends, which appears to be “clipping” the voltage to that maximum, thus giving you your doubled pitches. Since Mangrove has no such voltage clipping, it responds more how you’d expect.
That’s my guess anyway.
