Attempting to JIT compile method (....) while running with --aot-only.

Hi to all.

I am getting this exception when I process a WCF request from my Xamarin.Forms app:

"Attempting to JIT compile method '(wrapper runtime-invoke) :runtime_invoke_bool_Nullable`1 (object,intptr,intptr,intptr)' while running with --aot-only.
See http://docs.xamarin.com/ios/about/limitations for more information.\n"

Please, how could I fix this? I have checked the server side but it seems ok.

The rest of WCF requests are working fine and this only happens in devices (not in simulator).

Thanks.