If application runtime environment contains both Gen r8.0 (or prior) and Gen r8.6 .Net Proxy runtimes within GAC (Global Access Cache), you may get an error that references, CA.Gen.odc - Object reference not set to an instance of an object.
Unfortunately, there is no coding/PTF fix solution to this problem.
Primary recommendation is to upgrade the Gen r8.0 (unsupported) .Net proxies to Gen r8.6 .Net proxies and use only the Gen r8.6 runtimes in GAC.
Alternate recommendation is to separate the Gen r8.0 runtimes from the Gen r8.6 runtimes, in order to prevent the error from occurring. For example place the Gen r8.6 runtimes in GAC and the Genr8.0 runtimes in a local area cache (LAC).