Sync/Copy to SD Card not working?

[sunbuggies]

I have an odd configuration for storage on my phone - my internal storage is mapped to a partition on my SD Card, which has another partition still configured as external storage. I keep most documents and the like on the external partition, since I like to reserve the internal partition for apps and the like. However, RoundSync doesn't work on the external partition - all transfers give the output of either "0 files were downloaded" or "There was nothing to do". Scrolling back, it looks like the first time I tried to sync, it gave a permission denied error, but I've allowed RoundSync access to all files. It works fine when syncing/copying to the internal partition, so I've resorted to moving everything I want to sync to there for now. Any advice on how to fix this is appreciated.