"What Can I do in this case?"
- You can ignore the small variation in the peak heights. Does it matter?
- You can choose a sampling frequency that is an integer multiple of the ramp frequency. The ramp frequency is 1200 Hz, and your sampling rate is 500 KHz. For example, you could use a sampling rate of 480 KHz (), or 500.4 KHz (), etc. The sample y-values at the corners may not be exactly 0 and 5/6, depending on the phase angle of the sampling, relative to the phase angle of the sawtooth, but the y-values will all be the same, if you do that.
Good luck with your work.