Hello Infor experts and gurus! 
I hope this question belongs in this forum and that someone can answer it.
My MEC Mapper seems to "forget" the MappingUtils jar path shortly after I set it in a project's Configure Build Path:

When I do the above the annoying Java syntax errors in open functions disappear and all the references to MappingUtils objects and methods resolve correctly. Until I close and reopen a function -- then the syntax errors reappear and the jar is gone from the build path.
Am I doing something wrong or is my MEC Mapper somehow misconfigured?
Thanks in advance for your help!