What version of RUM Agent do you have? We have dynatrace across multiple clients and enviornments, users are using OSX and Safari in several versions. I've never seen such error, this is why I'm asking. If this happen on newest version of JS then you should rise support ticket.
since in the last year this post has been viewed quite often, we discussed this internally and I can give you the following answer to this.
According to our knowledge Safari in the past implemented the resource timings API but insufficiently, since they later removed it again. Since our way to capture resource timings works for IE, Chrome, and FF we believe that the error you experienced very likely occurred due to this insufficient implementation.
Nevertheless, we appreciate every stack trace that you can provide for us to dig deeper!
If you have users with such older Safari browser, then yes absolutely.
If they are newer versions please open a support ticket to give us the chance to look at this in detail.