See e.g., apparentPowerComputation_performInForeground() in com.itemis.embedded.platform.energy.implementation.impl.metrology.ApparentPowerComputationImpl
This problem relates to the (generic) units. If I remove all the unit stuff, then things work - so it is not generally a problem with int/int16 etc. in external modules.
See e.g., apparentPowerComputation_performInForeground() in com.itemis.embedded.platform.energy.implementation.impl.metrology.ApparentPowerComputationImpl