Cp contribution of methylenecyclobutane ring correction is bad

The Cp contribution of the methylenecyclobutane ring correction is very negative at high T:

entry(
    index = 17,
    label = "methylenecyclobutane",
    group = 
"""
1   [Cs,N] u0 {2,S} {4,S}
2 * [Cd,N] u0 {1,S} {3,S} {5,D}
3   [Cs,N] u0 {2,S} {4,S}
4   [Cs,N] u0 {1,S} {3,S}
5   [Cd,N] u0 {2,D}
""",
    thermo = ThermoData(
        Tdata = ([300,400,500,600,800,1000,1500],'K'),
        Cpdata = ([-3.91,-3.339,-2.739,-2.2,-1.51,-1.051,-62.52],'cal/(mol*K)'),
        H298 = (26.9,'kcal/mol'),
        S298 = (28.8887,'cal/(mol*K)'),
    ),
    shortDesc = u"""""",
    longDesc = 
u"""

""",
)

The overall thermo estimate for methylene cyclobutane ends up having a heat capacity of 0 at 1500 K, so I think it might have been a mistake when fitting.

I am currently recalculating this.