Error 500 when posting large form to windows azure from Android

Question

I have a HTML page with a form containing a large (>1400 character) hidden field value, that will not submit on Android browser to any site hosted on windows azure websites. I have tested this on 4.1 and 4.2 on different devices.
I have checked the error logs from Azure and am receiving a 500 error.
The page will submit from all modern desktop browsers, and iOS devices.
Unfortunately I can not provide a link to the actual page, as it resides under our companies extranet, but if I point the target of this simple form to any Azure website (*.azurewebsites.net) from an android device, I get the 500 error.
    <form action="http://*****.azurewebsites.net/" method="post">
        <input type="hidden" name="imageData" value="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"
/>
        <input type="submit" />
    </form>
To further test this I created a brand new site on azure websites, leaving everything as default. No code or anything uploaded (so you get the "This web site has been successfully created" page). Posting the form to this site gives a 405 response
(as expected), except for android that gives the 500.
Is there a setting or something I am missing somewhere?
Following up, I have identified this event in the error log if this helps:
138. GENERAL_READ_ENTITY_END
BytesReceived="0", ErrorCode="The I/O operation has been aborted because of either a thread exit or an application request.
 (0x800703e3)".

Answer 1

Originally I thought it may have been a browser issue, so I installed the latest Chrome and Firefox browsers as well, which all respond the same.
This is on 2 separate devices, both modern hardware running Android v4.1 and v4.2