The problem relates to the selection of insulation for the particular sections of pipe-runs and is signaled by the following diagnostic messages:
sized insulation thickness (%.1f mm) lower than specified (%.1f mm),
sized insulation thickness (%.1f mm) lower than required (%.1f mm).
These Warnings are displayed when there is no insulation of sufficient thickness in the selected insulation group. Note: the Warnings do not block calculations.
Solution
After clicking on the message in the Diagnostics window, the component that causes the problem is indicated.