Since you say that %include file contains macro code we now have a starting point. The behavior you describe is not uncommon for some types of macro problems.
With an interactive session I would open that %included source file and run one step at a time, macro definition, macro call, data step, procedure. That should identify a step that caused things to blow up. Then start with the fine tooth comb in that step for problem causers.
Before executing any macros, especially if these are new or modified from existing ones, I would be tempted to turn on the system options MPRINT SYMBOLGEN and possibly MLOGIC if you have lots of macro logic statements.
As far at the disappearing log is there any chance that the code codes any commands to clear the log?
I would also be tempted to use Proc Printo to direct log output to a file.
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