Thank you for contacting Rank Math and sorry for any inconvenience that might have been caused due to that.
I am sorry but some of the variables that you are using for your titles are reserved for use in posts and pages. The %tag% and %modified% variables will be used to get the current tag on the post and the modified time of the current post respectively.
At the moment, I have modified your title to the following which is displaying correctly %term% %sep% %sitename%
To get the tag modified time, you will need to create a new variable using the following filter: