How to diagnose the «Something went wrong while saving the customer» failure?

@dmitry_fedyuk There was an exception when I’m using it as a global event.

Here is my etc/events.xml

<event name="customer_save_after">
        <observer name="customer_save_after_handler" instance="MyCompany\MyModule\Observer\MyClassName"/>
</event>

And it come up with an exception: Something went wrong while saving the customer.
Do you know what happened?

The «Something went wrong while saving the customer» message is generated here:

As you can see, an actual exception is not logged.
You should log it here or set a breakpont.