I have noticed that in v9 we do not always see the error message thrown at the server. In these cases the user gets no response, except that the state of an object does not change or some other implicit way to see that something is wrong, but the original error message is eaten away somewhere.
I am wondering is this a bug, or is it dependent of some user group or setting, debug mode, or something else?
Looks like Error message are written into the log file, check your config file.