I did some testing regarding #1217 and found out that some actions like ModifyEntity and ModifyProperties undo their actions after server restart. I assume it's a bug.
Magic 10.8.8-378a107 & paper 1.19.4 if it helps, also you can find spell examples in #1217

Just adding that it happens to 'ModifyAttribute' on mobs too- Here is a mob's Attributes (applied with ModifyAttribute) after;

Initial generation

Magic Load/ Config Reloads

Server Restarts

As intended, H through S are applied randomly 0-12, and RGB are random colour values 0-255
(Paper 1.19.4, and Magic 10.8.9 Snapshot - bced71e)