this is known issue and was already fixed in last betas.
pls update uROWebBrokerServer.pas as
function TROWebBrokerServer.ReadRequestStream(aRequest : TWebRequest): TStream;
...
begin
{$IFDEF DELPHIXE10UP}
aRequest.ReadTotalContent; // added
SetString(s, PAnsiChar(@aRequest.RawContent[0]), Length(aRequest.RawContent));
{$ELSE}