The ADS comment character ("!" by default), is defined in the SYSGEN ADSO statement.
In order to use ADSOBCOM, a valid ADSOOPTI module containing the ADS options must be present.
Occasionally, the offsets of some of the parameters may change from release to release and so if you have an obsolete ADSOOPTI, ADSOBCOM compiles may not work as expected.
This has happened in the past to the comment character, and as such, ADSOBCOM will not know what the correct comment character is and compiles that work online in ADSC will fail unexpectedly.
CA IDMS, all supported releases.
Use the ADSOBSYS utility to generate a valid ADSOOPTI module for the current release, and use that module in the ADSOBCOM compile step.