Just got this in the mail.
"Greetings Pfeffernusse,
Thanks for reporting this to us.
Unfortunately this issue can occur and some mobs can spawn 'underground' making you unable to attack them. Do you see this only in certain areas or all over?
If you are seeing this a lot it maybe worth running the Repair function from the launcher. This will check for and repair any corruptions in your game files, you can find this by logging into the launcher and clicking the cog icon. This may not solve the issue as it could be the other issue I mentioned above.
I would also advise using the In-Game tool to make a bug report concerning this issue.
Thanks for your patience.
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There may also be other replies, but you will not receive any more notifications until you visit the forum again.
All the best,
STAR WARS: The Old Republic"