Features Service Not Working for Many Accessions

[Andrew Simmons]

I recently began using the features service of the Proteins REST API, and noticed that most (but not all) of the accessions that I entered yield an output consisting of an empty set of brackets ([]).

The following are examples of accessions for which no features were yielded:
P25105
Q96G27
Q7Z418
O43731
O75635

I know that these accessions do in fact have features that are listed on their respective pages. Furthermore, using the search function in the UniProt class of the BioServices python library yields the features for those accessions.

Am I missing something? I've tried setting and changing many different values, to no avail. Why does using the features service not return the features for so many accessions?