That looks like a bug.....
I *think* (not sure) it should be checking the path until the last "\", looks like it checks until the first "{".

I will look into it for the next release. For the moment, it should work if you apply a different dynamic name like
E:\FTPRoot\WatchFTP\MarketForce\Inbound\{filetitle}_rascal.edi
or
E:\FTPRoot\WatchFTP\MarketForce\Inbound\rascal\{filetitle}.edi
(and obviously, create the rascal subdirectory)