Now, I'm aware that Compound Splitters isn't being maintained any more, but it does still work in 1.0 with just the version number changed. However, with this mod installed, any Compound Splitter will only have the output speed of a single belt regardless of how many belts are fed into or out of it. I could provide a save file if needed.
edit
Actually, scratch that - I may have misidentified the source. Will investigate, but removing your mod completely still keeps the issue. I was missing a variable on my end. Apologies.