When loading an existing project originally created on Kdenlive/Linux, with many image clips, Kdenlive on Windows does not correctly loads (refreshes?) the images. Instead, the clips in the timeline are shown either as invalid or as pure white frames. Manual reloading each clip in the project bin causes the image to be correctly reloaded. However, on opening a project this does not work. Also saving and reloading the project does not remedy this situation. This is always reproducible for me.
This happens with all projects of mine: I'm using lots of still images and thus these projects need many image producers. After loading these projects, the project bin correctly shows thumb images. However, the clip monitor only shows a white image, instead of the correct image. Also, these clips in the timeline only show white frames. Reloading each project bin clip then gives a correct image ... but is a pain in the back, considering projects with 50-100 individual image clips.
Should be fixed with Kdenlive version 17.12 Please try with the actual Kdenlive version 18.08.1