I do not have the switchblade model, so I can only guess that the behavior in question is due to either (or both) of the following:
A) Exceeding inlet, EGT, or oil temp settings
b) Operating for an extended time in excess of 105% RPM
To illustrate those effects here, I have my own flight model for the MiG-25PD. In real life, the maximum permissible speed with a war load (according to published sources), is Mach 2.83. The aircraft easily attains that velocity at 45,000 feet and 102% RPM:
http://forum.combatace.com/uploads/1172413...9_43_107485.jpg
At 107% RPM, it is possible to hit Mach 3.2 in clean configuration (or, in this case, Mach 3.07 with a war load), above 50,000 feet. However, as in real life, those engines will only attain that air speed once
http://forum.combatace.com/uploads/1172413...9_43_127061.jpg