UC1843A-SP: RT/CT Sawtooth Waveform in SPICE Model Hits Zero

Tool/software:

I noticed using the UC1843A-SP model in SIMetrix that the sawtooth waveform on the RT/CT pin goes from 0V to 2V instead of about 1V to 3V, like the UC3843 model. This doesn't seem correct because the 2N2222 NPN doesn't turn on between 0V and about 0.7V, preventing the PWM from operating in the first 30% of duty cycle or so. I am using a configuration similar to the Open-Loop Laboratory Test Fixture (Figure 26) in the datasheet.