On our mono deployments JSON returned from service was cut in half.
Does not affect windows deployments.
Mono JIT compiler version 4.8.0 (Stable 220.127.116.110/8f6d0f6 Wed Mar 15 16:18:35 UTC 2017)
Revert to 4.5.6 helped, I don't have time to reproduce this today, sorry.
I can prepare example project tomorrow if necessary.
This should be fixed by this commit and this fix is available in v4.5.9 on MyGet. Can you check this version and tell if the fix working for you?
It is working now, thanks!