Uh, maybe stupid question, but wouldn't drawing sprites in order from north tiles to south tiles (so that northern tiles are covered by southern tiles) fix the most egregious issues ? That's how it is done and it really solves the most egregious issues ... for example notice how the vertical walls ...

Version: 0.17.6 (build 43339, win64, steam)
Splitter (normal) image layer is under Wall image layer. Should be above?
Other Splitter types not tested. (not researched )