Cracking LTspice model encryption is *NOT* something we can safely discuss here. L.T. (now Analog Devices) historically have been tough on anyone disclosing what they regard as proprietary data, and it would not be fair to bring that level of legal scrutiny down on our host Dave's neck!
@Anyone: If this offends your belief in a right to free speech, are you willing to put your money where your mouth is and provide Dave with a large enough legal defence fund to go up against A.D's corporate legal team?@Glenn,
Therefore the only legal way forward to get insight into the OnSemi model internals is to work with OnSemi's product support team. First try any test jigs they show in the datasheet and if any of them have similar sim issues, send them the .asc file and ask what you are doing wrong. If their test jigs sim O.K. try simplifying your circuit until you get a minimal one that has the problem, then submit that to them for comment. If you have any personal contacts at OnSemi reach out to them for how to escalate to whoever actually writes the models. Also you could try begging for an unencrypted model, hopefully not under a NDA so you are free to discuss it here.
Unfortunately the link you provided was to models and symbols for NGTB25N120FL3WG, not the NGTB25N120S in your 'Draft6.asc' sim. I've just found the latter here:
https://www.onsemi.com/products/discretes-drivers/igbts/NGTB25N120SI'll give it a try later today and see if I can reproduce your problem and find any workarounds.
So far, I have noticed that the .ic command for L1 current isn't being applied (no uic option in the .tran command) and also has an inappropriate space between the I and the (. Also if you want that current to actually 'take' you need to set it as an initial condition for *ALL* the inductors in the loop it will be flowing through via the U2 body diode before U1 first switches on.
Its possible that issues with the model's internal diode could be 'patched' by adding a suitable external diode in parallel.
General LTspice hints:
Multiple SPICE dot commands can be placed as a single item on the schematic. Ctrl-Enter starts a new line in the dot command edit dialog, and it also accepts blocks of text complete with line endings copy/pasted from external text editors etc. This is particularly useful for stuff that should be kept together e.g. multiple .measure or .option commands, that you can then enable or comment out as a block
Also, with a very slow or glitchy sim, you may well want to move your .measure statements to a separate file and .include it rather than putting them directly on the schematic, as then you can edit and re-run them by
File:Execute .MEAS script with the waveform subwindow in focus without having to rerun the sim.