The Feedthrough.fmu (for FMI 2.0, version 0.0.30) reports communicationPoint mismatches at random times in the simulation. For example:

Expected currentCommunicationPoint = 11958.34 but was 11958.35.

The CoSimulation runs with a fixed step size of 0.001s. The master calculates the communication point by iteration * h i.e. no numeric noise is accumulated. If this is a problem due to numeric inaccuracies, I would expect the error to appear always at the same time in the simulation (once the added-up inaccuracies have become larger than some threshold). However, this is not the case. The problematic communicationPoint is different each time the simulation is run.

At first I thought that there might be a problem with my simulation master implementation but when I run the FMU in FMPy, it shows the same problem. Hence, it's more likely that the implementation in the FMU is not correct or not tolerant enough.