Simultaneous Heating and Cooling problem with LowTemperatureRadiant:Constant Flow

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I have a building model with a LowTemperatureRadiant:ConstantFlow element providing either heating or cooling to a zone. Further 5 plant loops are included (primary and secondary loop for heating and cooling and one more for the icewatertank on the cooling side) When running the simulation cooling and heating are often provided simultaneous (mostly in summer), and following warnings/errors are given:

1. Plant Loop: SEC HW LOOP Demand Side is storing excess heat the majority of the time. (Warning is given for all loops).

2. CheckWarmupConvergence: Loads Initialization, Zone="LEVEL0:0.09VERGADERZAAL" did not converge after 50 warmup days.

3. SimHVAC: Maximum iterations (50) exceeded for all HVAC loops, at WINTER, 01/02 09:30 - 09:45 ** ~~~ ** The solution for zone HVAC equipment did not appear to converge.

Which I think has to do with the operation schemes & control of the loops. I tried running with only heating or only cooling loops operational. When turning off the cooling loops, the warmup convergence issue is not a problem anymore. When turning off the heating loops, heating is however still provided by the radiant element. How can this be possible? Is there a good way to define all these operation schemes in a proper way or a way to find the issue?