Visual Voicemai Error — Not Enough Memory

When I try to use the Visual Voicemail app I get a warning that there is not enough memory with no additional information. The T-Mobile website recommends having 15% of one's memory free to run the Visual Voicemail app. Neither specifies whether they are referring to storage/disk memory or RAM. I am assuming it means storage memory, however I still have some questions. 

As for storage memory, a hard and fast rule of 15% is sort of useless as devices all have differing storage amounts. I have a micro SD card inserted for extra storage and can get a larger card whenever to free up space if Visual Voicemail requires internal storage space. As there is no information about what the error means or where space is required, it is difficult to know whether this will help. 

Also, the app seems to consistently have issues creating transcripts of messages and doesn't text/email my messages like the old Sprint visual voicemail feature did. That is frustrating for an app called "Visual" Voicemail.

Both of these issues along with activation issues dominate the app reviews in the Google Play Store for the last few weeks and looks like it goes back to July. Some people report getting the memory error on new devices which seems old and sounds like device/Android version problems rather than a storage issue. The app's rating has dropped to just 2.6★ of 84,113 reviews with about 60% being one ★. 

Finally, and this one should go without saying, people must be able to forward the recording to storage by either saving them to their phone, sending them to email, or sharing a link that they can download on another device. The reviews are littered with folks who have lost messages from deceased loved ones when instructed to delete and reinstall the app. As many of the complaints also discuss difficulty with transferring messages or inconsistent responses from support about whether deleting will destroy such messages, it really needs to make clear how to backup the messages securely or guarantee them in a better way during support encounters. 

Are there plans to address these ongoing issues with Visual Voicemail? If so, what is the timeline to do so? Will it be equally fixed for all phones currently supported by the company?