I saw some similar issues reported, but couldn't find one which was exactly the same. Editing the NBT of a painting in any way at all seems to cause it to jump upwards (and sometimes to the right too). Tested with the following:

execute as @e[type=painting,limit=1] run data merge entity @s {Glowing:1b}

execute as @e[type=painting,limit=1] run data merge entity @s {Invulnerable:1b}

The bug only seems to occur for certain painting sizes however; for example, 1x1 and 2x1 paintings are unaffected while 2x1 and 4x4 paintings are.