Deadlock when synchronously opening connections from the thread pool

Threads (wait for image to load):
<img src="https://www.dropbox.com/s/dns6hwc1eq1w6xk/saga_db_problem.png?dl=1">

I use NHibernate with Npgsql 3.1.5.0 and when testing with high load sometimes server is completely blocked by this exception.

Can I expect a fix on your side?
