So it had nothing to do with the calibration after all.
I had updated and downgraded JMRI versions so many times over the course of a decade on this hard drive that JMRI was getting confused and throwing errors looking for files that weren't there until it crashed.
So a clean install and removing the 4 to 5 file locations that had been created over the years worked.
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A 32 bit compatible JMRI version and Java seems to do the trick.
Further experimentation may reveal which version is the highest for that.
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