Armor Stands with the Marker tag are not supposed to be interacted with, but they can be pushed with the AOE knockback effect of "fully charged" sword swing. However, if the NoGravity tag is also enabled, the knockback effect doesn't happen.
I've recorded a short clip showing how to recreate the bug:
https://youtu.be/wEsXEo4qk1Y
Related issues
duplicates
Comments

Duplicates/relates to MC-75197.