Steps to Reproduce:
1) Open a super flat world (so it's easier to reproduce)
2) Run

/tp @s 1000 ~ 1000
/summon pig
/give @s saddle

3) Ride the pig and run

 /summon lightning bolt

4) You will be sent to coordinates (0, 1.4, 0) and console logs:

UUID of added entity already exists: arn['Shuddery'/717, l='ServerLevel[New World]', x=0.00, y=1.40, z=0.00] 

5) Save and quit world and rejoin to see yourself on the zombified piglin now