Hey There,
Thanks for writing in with a great question! Capitalization definitely shouldn't matter to our crawler or to Google, so I looked into this keyword with one of our devs and it looks like the rankings for "jobmesse" was collected about 16 hours before the rankings for "Jobmesse" so we believe this is actually a natural fluctuation in the SERP for this keyword. I manually check the current rankings for both version of the keyword, I am seeing that your site currently ranks at #11 and the keyword has a difficulty score of 56%, so it is definitely within reason to see fluctuate in a matter of hours between the rankings.
I hope this helps. Please let me know if you have any other questions.
Chiaryn