Some Strange Behavior From a Hegel 360

OK, here’s a strange one- please jump in. Just purchased a Hegel 360 to power my Revel 228s. Upper bass was excellent. Lower bass strangely lacking.   With the same recordings a good friend was getting much better bass with his Kinke Studio EX-M1 and 1.7 Maggies which aren’t known for their deep low end.  We ran his amp through my system and the bass was robust but clearly defined as it should have been- so no problem with cables, other components or speakers. Double checked all connections with the 360- everything was fine. My friend suggested we switch polarity via a speaker connection. The difference was rather amazing. Bass was now there and overall sound improved significantly- almost the opposite of what you’d expect. Any thoughts? On a related note, I’ve contacted Hegel a number of times about this issue- no response. The only support link I can find is the general info@Hegel link on the Hegel website. Any thoughts on Hegel tech support or ideas on reaching them? Thanks for your thoughts...