Reproduction:

<telerik:RadMediaPlayer RenderMode="Lightweight" ID="RadMediaPlayer1" runat="server" AutoPlay="true"
Height="360px" Width="640px">
    <PlaylistSettings YouTubePlaylist="PL28149B23F489D223" Mode="Buttons" ButtonsTrigger="MouseDown" />
</telerik:RadMediaPlayer>

WebVTT file with a text header is not being displayed and cues with identifiers are also not shown.

Not working sample .vtt file:

WEBVTT - This file has cues.

14
00:01:14.815 --> 00:01:18.114
- What?
- Where are we now?

15
00:01:18.171 --> 00:01:20.991
- This is big bat country.

Working sample .vtt file:

WEBVTT

00:01:14.815 --> 00:01:18.114
- What?
- Where are we now?

00:01:18.171 --> 00:01:20.991
- This is big bat country.

• Web Video Text Tracks Format (WebVTT)
• WebVTT: The Web Video Text Tracks Format - 1.4. Other caption and subtitling features

RadMediaPlayer requires multiple taps to play videos in Safari in IPad. The problem is not reproducible in other mobile browser.

Steps to reproduce:
1. Open http://demos.telerik.com/aspnet-ajax/media-player/examples/overview/defaultcs.aspx  in Safari in iPAD
2. Tap to play the video

Result: The video will be not played on the first tap. 

Using the 2015 Q2 version, there will be no error when the playlist is invalid. The RadMediaPlayer playlist will remain empty, and you can handle the PreRender event if you want to do further configurations