The Bug
Experience Orbs within spawners are 2D which is inconsistent with other entities in spawners which are all 3D. This causes them to be small and un-viewable at certain times during there rotations.
/setblock ~ ~ ~ spawner{SpawnData:{entity:{id:"minecraft:experience_orb"},Delay:1s}}
Hi there!
I can confirm for snapshot 20w30a and release 1.16.1.