tSQLt Test Adapter failing with an exception error

tSQLt Test Adapter for VisualStudio 2015 Update 3 stopped working with the error message which is below. I wondering is there a way to solve this, maybe some of the configurations are not correctly set. The most intriguing thing, that another project which has same setup of tSQLt tests works perfectly with the same VS and adapter.

-- tSQLt Test Adapter
v0.70

-- RUNSETTINGS FILE:

-- ERROR MESSAGE:
------ Discover test started ------
tSQLt Test Adapter, searching for tests...
tSQLt-Test-Adapter: Adding filter: Tests
An exception occurred while test discoverer 'tSQLtTestDiscoverer' was loading tests. Exception: Object reference not set to an instance of an object.
========== Discover test finished: 0 found (0:00:00.253) ==========

-- Folder structure
+ Tests
+ up_Test
-- up_Test.sql ( test schema)
-- test 01 test name.sql (test sp)
[....]