The bug

With the fix of MC-207605, you can now remove the Owner tag from a tamed wolf or a tamed cat using the /data remove command. However if you do that while the tamed wolf/cat is sitting, the mob while stay in sitting mode forever making it unable to move unless you hit it or you relogging. 

How to reproduce

• Tame a wolf with bones
• When the wolf is tamed it will sit by default
• Use the following command :

/data remove entity [wolf UUID] Owner  

-> The wolf while stay in sitting mode forever

Observed Behavior:

Wolf/cat is motionless.

Expected Behavior:

Wolf/cat while still move but sitting at the same time since we didn't remove the Sitting tag.