That would require an unlikely 63 degree helix angle. With a more reasonable 25 degrees it probably looks like this.
@Moded1952 Is it possible that the cutter impacts are acting as impulses exciting workpiece/machine resonances (“ringing the big bell”)? Maybe measure the machine’s impulse response?
@spargeltarzan’s calculator predicts “High tool stress”. Do you think that overheating is also causing and/or contributing to the endmill damage?