I've made a few tests and printouts to splot where the evaluation is failing when using CompactSplines. Here is the printout.
13/05/2023 15:34:24 [EventDialCache]: Invalid dial response:
13/05/2023 15:34:24 [CompactSpline]: d43 = -nan
13/05/2023 15:34:24 [CompactSpline]: data[2+d43_1] = -nan
13/05/2023 15:34:24 [CompactSpline]: dim = 4
13/05/2023 15:34:24 [CompactSpline]: d43_1 = 2
13/05/2023 15:34:24 [CompactSpline]: d43_0+1 = 2
13/05/2023 15:34:24 [CompactSpline]: ix+1 = 1
13/05/2023 15:34:24 [EventDialCache]: CompactSpline: input({ Cross-Section Systematics/#57_MPi_Multi_Shape=0 }) supervisor(minResponse=0, maxResponse=100) response=-nan
13/05/2023 15:34:24 [EventDialCache]: CompactSpline: spline data = { 0, 1, 1, 1.667 }
13/05/2023 15:34:24 [EventDialCache]: CompactSpline: defined bounds = { 0, 1 }
13/05/2023 15:34:24 [EventDialCache]: CompactSpline: allow extrapolation ? 1
13/05/2023 15:34:24 [EventDialCache]: CompactSpline: EVAL MANUAL at 0:-nan