Using the extra info from Dinesh, here's what I did to investigate. Admittedly I was on a 2015.1.0 Ensemble on Windows, but the classes are unlikely to have many differences between this and his 2015.1.2 on Solaris.
First I cleared the read-only flag on the CACHELIB database that stores %Net.HttpRequest:
Then I loaded the class into Studio (for safety I set the read-only checkbox during opening), compiled it, used the View\View Other Code option (Ctrl+Shift+V) and jumped to the line of the error Dinesh reported.
I reset the "Always Mount Read-Only" checkbox on CACHELIB, to prevent accidental changes.
In the code several things caught my eye:
Maybe disable the GZIP feature on your SOAP adapters and see if the problem persists. Searching the InterSystems doc for the term GZIPOUTPUT may give you clues (I'm no expert in this area).
I also recommend you ask InterSystems Support (WRC) for help on this, particularly as you're running on a less common platform (Solaris).