I installed the R2018b Update3 yesterday and when I checked just now, it said that I was running the latest update.
I suggest you do the update again. If you continue to have problems, sue the Contact Us link in the upper right corner of this page to request MathWorks Technical Support. (If you do that, run the ver command from your Command Window or a script first. You will need to paste the results to a window on the Technical Support request page.)
Note: If I remember correctly, you must have previously installed the first two updates. If you did not install the first update, you may have to un-install and re-install MATLAB 2018b, then do the updates.