The test page uses an old version, which may actually be useful since it illustrates that the order of lookups is important.
There is a previous thread discussing the topic of OpenType Feature precedence.
My latest version of Mandala does not suffer from the above problem. However, I did not yet find any way to avoid the conflict between fractions and ordinals.
Feel free to download my Mandala font and see if you can come up with a solution. The linked thread would be a good place to report your findings.