The issue is that your are experiencing thermal runaway. See this note in the PLECS Error Messages documentation, which highlights the same issue albeit which can manifest in different errors. I can see that some of your FETs hit a temperature of 1e14 degrees, upon which the error occurs.
The issue is in the MSC020SMB120DS model you have developed. Unfortunately that part doesn’t have a PLECS model and I’m not certain how you developed the associated model as the data sheet is missing several key parameters. However a very similar part does MSC020SMB120B4 have a PLECS model provided by Microchip. Perhaps compare the two devices and determine if that is a suitable replacement. Even so, a “good” thermal model can experience thermal runaway under extreme operating conditions.