MMS API glitches

We've been doing testing of the new MMS API and are finding a few issues with attachments.

1. Inbound .mp3 attachments (audio/mpeg) never arrive.

Instead, an SMS message with no subject and no binary attachments is received. For example, this was an inbound .mp3 file from an AT&T subscriber (myself):

{
"uri" : "https://platform.ringcentral.com/restapi/v1.0/account/540887020/extension/2410069012/message-store/789154283012",
    "id" : 789154283012,
    "to" : [ {
      "phoneNumber" : "+13056151181",
      "location" : "Keys, FL"
    } ],
    "from" : {
      "phoneNumber" : "+17865255158"
    },
    "type" : "SMS",
    "creationTime" : "2017-06-03T16:13:02.000Z",
    "readStatus" : "Unread",
    "priority" : "Normal",
    "attachments" : [ {
      "id" : 789154283012,
      "uri" : "https://platform.ringcentral.com/restapi/v1.0/account/540887020/extension/2410069012/message-store/789154283012/content/789154283012",
      "type" : "Text",
      "contentType" : "text/plain"
    } ],
    "direction" : "Inbound",
    "availability" : "Alive",
    "messageStatus" : "Received",
    "conversationId" : 1344640119899243546,
    "conversation" : {
      "id" : "1344640119899243546",
      "uri" : "https://platform.ringcentral.com/restapi/v1.0/conversation/1344640119899243546"
    },
    "lastModifiedTime" : "2017-06-03T16:13:02.167Z"
 }

2. Outbound .mp3 attachments (audio/mpeg) arrive apparently downsampled and with poor sound quality.

Prior to posting to RingCentral's API, our application converts outgoing attachments to and then from Base64, but I don't suspect this to be the issue.

3. Outbound .zip compressed attachments (application/zip) are never received.

Instead the smart phone recipient (in this case an AT&T subscriber iPhone 7 running iOS10.x ) gets this message:

One or more of the message components have been deleted by MMS Adaptation. Either the message was too large or the components were unsuitable for your handset.

Are there platform-specific issues around certain contentTypes such as zip compressed files? Example outbound .zip file:

https://media.ringcentral.com/restapi/v1.0/account/540887020/extension/2410069012/message-store/788625869013/content/37874117013

4. Inbound .mp4 videos (video/mp4) are being converted to 3gp and downsampled to extremely low resolution/quality.

For example, this video was downsampled from 604 Kilobytes to 64 Kilobytes:

{
"uri" : "https://platform.ringcentral.com/restapi/v1.0/account/540887020/extension/2410069012/message-store/789217075012",
    "id" : 789217075012,
    "to" : [ {
      "phoneNumber" : "+13056151181",
      "location" : "Keys, FL"
    } ],
    "from" : {
      "phoneNumber" : "+17865255158"
    },
    "type" : "SMS",
    "creationTime" : "2017-06-03T22:24:54.000Z",
    "readStatus" : "Unread",
    "priority" : "Normal",
    "attachments" : [ {
      "id" : 789217075012,
      "uri" : "https://platform.ringcentral.com/restapi/v1.0/account/540887020/extension/2410069012/message-store/789217075012/content/789217075012",
      "type" : "Text",
      "contentType" : "text/plain"
    }, {
      "id" : 189966622012,
      "uri" : "https://media.ringcentral.com/restapi/v1.0/account/540887020/extension/2410069012/message-store/789217075012/content/189966622012",
      "type" : "MmsAttachment",
      "contentType" : "video/3gpp",
      "size" : 66006
    } ],
    "direction" : "Inbound",
    "availability" : "Alive",
    "subject" : " ",
    "messageStatus" : "Received",
    "conversationId" : 1344640119899243546,
    "conversation" : {
      "id" : "1344640119899243546",
      "uri" : https://platform.ringcentral.com/restapi/v1.0/conversation/1344640119899243546"
}