Does the part package if you have all symbols on the same sheet? The error indicates a symbol is missing. Having devices across sheets should make no difference.
What kind of 'Hetero' is it?
Type 1 - Mixed gates (example a device with three and gates and one inverter)
Type 2 - Implicit and explicit power pins (example Op Amp with one symbol showing the power pins and one symbol just the gate)
Type 3 - Split IC - a number symbols making up the complete part with different number of pins in each
Type 4 - Two representations of the same part - single gate and full package for example (resistor vs resistor pack)
Thanks for the reply Robert,
Problem solved, it was Type 3. since it was a imported doc I wasn't too familiar, but I noticed they have different partition values so I added partition name before the sym name in Hetero as "partitionname:sym_name" and it worked.
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