Can't use item on mob after riding another mob

Partner Rank: 3

Verification builds: 1.16.200, 1.14.60
Regression builds: Unable to test earlier than 1.14.60

Summary: After riding a mob, you can't use certain items while looking directly at a mob

Impact: This makes combat mechanics in an upcoming map seemingly unresponsive

Repro Steps:

1. Download and open the attached world
2. Look at the pig and use the snowballs
3. Ride the cow and dismount
4. Look at the pig and use the snowballs again

Expected Results: Snowballs are thrown both times

Observed Results: After riding the cow, snowballs can't be used while looking at the pig

Screenshots/Videos attached: Yes