Hilbert Transform, filters - two different phase graphs

Relationship between magnitude response and phase response for minimum phase is:

Phase plots are obtained from Hilbert transform of real magnitude values. Input to Hilbert transform was a vector (array) of real magnitude values in dB. Magnitude vs. frequency (Fig. 1.) is a raised-cosine function defining a Mesa filter with plateau.

I obtained phase values in two ways. In Fig. 2. the resulting phase plot (phase from the previous formula, not the phase from analytic signal) is obtained from SciLab using command x = -hilbert(xr), printing imag(x). Variable xr is vector holding magnitude values. In Fig. 3. the phase plot (phase from the previous formula, not the phase from analytic signal) is obtained from C implementation of Hilbert transform taken from ht.c file on the web. Hilbert transform here is implemented as convolution and the values are in xh[i].

Although similar, the phase plots on Fig. 2. and Fig. 3. are quite different. Any insights why I am getting two different graphs of phase?