1217: overlay vector corrupted during execution
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 This message indicates that the overlay manager has detected an invalid
 overlay vector. The most likely cause of this is corruption at runtime due
 to an invalid pointer or attempting to overlay a non-overlayable module.

 Another possible cause is the use of a debugger to place breakpoints in the
 code after an overlay call, since this replaces the vector data with a
 debugger breakpoint.

 Use of the MURPHY command for debugging overlays may help to identify
 whether non-overlayable modules are responsible for this message.