I’m also not convinced that this is causing the problem, but the path to figuring out mysterious issues is to systematically rule out every remote possibility until only the real cause remains 
So I fully agree with your approach here.
I just thought it makes sense (for any future readers happening upon this) to clarify the purpose of DNS because there’s too much confusion already in this thread.
(And generally, people are dicking around with IP addresses way too much, creating problems on the way that aren’t necessary, although DNS was put into service in 1985 (and RARP in 1984, followed by DHCP in 1993) precisely to avoid the confusion caused by dicking around with IP addresses. )