Tamed wolf ownership cannot be transferred via commands

I tried transferring a tamed wolf from my friend's account to mine on a vanilla private server.

I used this command:
/data merge entity @e[type=wolf,distance=..10,limit=1]

{Owner:"DNLPLAYZ"}

the output was: " modified entity data of Wolf"
but i cant make it stand or sit

So i tried doing it using a different command:
/data merge entity @e[type=wolf,nbt=

{OwnerUUID:"OldOwnerUUID"}

,distance=..10,limit=1]

{OwnerUUID:"NewOwnerUUID"}

but it said something on the lines of the entity not existing