Diverging marginal curves

Trying to fitSurface with alternative Loewe null model, I get diverging marginal curves error. Staring at the curves they do not seem to diverge. In one of my attempts to debug, it appeared as if the harbronLoewe somehow receives different coefficients than those present in MarginalFit object. Could be some issue with 4PL asymptotes (see two alternative ways to make the issue go away in reprex below), if that makes any sense.

foo = structure(list(effect = c(3.1, 2.3, 1.1, -0.2, -0.7, -1.9, 3.3, 
3.2, 1.9, -0.4, -1.6, -2, -3, -3.8, 0.1, 0, -1.4, -2, -3.2, 3, 
2.4, 1.2, -0.2, -0.6, -1.7, 3.2, 3.2, 2, -0.3, -1.5, -1.8, -3.1, 
-3.9, 0.1, 0.1, -1.2, -2, -3, 3.2, 2.6, 1.2, 0.1, -0.4, -1.7, 
3.3, 3.2, 2.1, -0.2, -1.2, -1.5, -2.7, -3.7, 0.2, 0.1, -1.1, 
-1.9, -3), d1 = c(0.01, 0.1, 0.3, 1, 10, 20, 0, 0, 0, 0, 0, 0, 
0, 0, 1, 1, 1, 1, 1, 0.01, 0.1, 0.3, 1, 10, 20, 0, 0, 0, 0, 0, 
0, 0, 0, 1, 1, 1, 1, 1, 0.01, 0.1, 0.3, 1, 10, 20, 0, 0, 0, 0, 
0, 0, 0, 0, 1, 1, 1, 1, 1), d2 = c(0, 0, 0, 0, 0, 0, 0.01, 0.1, 
0.3, 1, 3, 10, 30, 100, 0.01, 0.1, 1, 10, 30, 0, 0, 0, 0, 0, 
0, 0.01, 0.1, 0.3, 1, 3, 10, 30, 100, 0.01, 0.1, 1, 10, 30, 0, 
0, 0, 0, 0, 0, 0.01, 0.1, 0.3, 1, 3, 10, 30, 100, 0.01, 0.1, 
1, 10, 30)), row.names = c(NA, -57L), class = "data.frame")

## quick fix
#idx = with(foo, d2 == max(d2) & d1 == 0)
#foo[idx, ]$effect = foo[idx, ]$effect * c(0.8, 1, 1)

bar = fitMarginals(foo)

## alternative fix
#bar = fitMarginals(foo, fixed = c('h1' = 1, 'h2' = 1))

plot(bar)  # not diverging marginal curves
set.seed(1)
baz = fitSurface(foo, bar, null_model='loewe2', 
  statistic = "both", B.CP = 5, parallel = FALSE
)

Error in harbronLoewe(doseGrid, fitResult$coef) : 
  Alternative Loewe generalization does not work for diverging marginal curves.

Ubuntu 18.04.4, R 3.6.3, BIGL 1.4.3

openanalytics / BIGL

Diverging marginal curves #4