Behaviour:
When a user changes the value of the Components or fix/affected version field of an issue in a TMP or a CMP from value 1 to value 2, the issue history shows 2 entries-

1. Change from Value 1 to none
2. Change from None to Value 2

Both the history entries may or may not be in the same sequence.
 
Cause: 
By design, issue history shows entries individually for each version.

Even though the user actions in UI are sequential, the request made to the back-end was a single request, so that's why the two entries have the same timestamp and can appear in 1-2 or 2-1 sequence. 

Suggestion: 

It would be great to have a single entry for change in the fix/affected version.