same thing for me since 1.5.0
So now i only working in savemode = 1. and only when finishing my project i save my samples as .ch1 (savemode = 2)
not happened with all my samples, but some of them.
if you open your samplemap (.xml file) and resave it with save 1, you''ll open it again with old .wav (or else format) samples. Not lost