Secondary outputs not available for in-memory connection

The following code fails with itk::ERROR: InputImageListParameter(0x1c664d0): Image number 0 is null. Please check the upstream source:

import pyotb

img = "https://gitlab.orfeo-toolbox.org/orfeotoolbox/otb/-/raw/develop/Data/Input/SP67_FR_subset_1.tif"

ms = pyotb.MeanShiftSmoothing(img)
filt1 = pyotb.Smoothing(ms["fout"])
filt2 = pyotb.BandMath(ms["foutpos"], exp="im1b1")
filt1.write("/tmp/filt1.tif")
filt2.write("/tmp/filt2.tif")

I have switched downstream apps, to check that it is not an issue with bandmath. The bug persists