Hello,
I create a Minecraft map, I encountered difficulties with the effect of regeneration potion on modified villagers "/give @p spawn_egg 1 0 {EntityTag:{id:"minecraft:villager",Profession:5,CustomName:"Level 1",CustomNameVisible:1,Health:4,Attributes:[{Name:"generic.movementSpeed",Base:0f}],Silent:1}}". This video shows the different steps taken.
https://youtu.be/EYoZzfFeb84