References no longer numbered as entered

As I entered my references, I wrote the refman number down and filed accordingly.  Since beginning this database, I have changed computers and OS which both resulted in a reinstall of the program.  At some point, Refman reorganized my references so the ref number is different.  I noticed when I sorted by number that the older entries are in alphabetical order.  This means that about 120 of my references are incorrectly numbered in my file.  Why did this reorder my entries?  I can change the number but want to know what went wrong so it doesn’t happen again when I have many more entries.  This is version 11.0.1.

Feeling a little frantic right now!