The boss bar doesn't show up when creating a custom wither

Partner Rank:

3

Partner Team Reporting:

Jigarbov productions

Verification builds and Platforms:

1.12.0.27, 1.12.0.25, 1.13.0.2, Minecraft-Release_UAP_x64_2693265 - 1.13.0.4 RC2

Summary:

"Add entity" wither doesn't have the boss bar when spawned

Impact:

Makes the add entity feature unreliable and forces us to edit behaviors on existing mobs which causes problems with backward compatibility in the long run and not a best practice.

Repro Steps:

1. Download The RP and BP attached to this report
2. Create a new world with these packs
3. get the "customwither" egg or do /summon jig:customwither
4. look at it

Observed Results:

The wither will start it's spinning animation but there will be no boss bar

Expected Results:

there should be a boss bar

Screenshot/Video?

see above

Regression Builds:

Tested it across 1.12 and 1.13 and it didn't work. Didn't test earlier than that, but add entity is a new feature.

Notes:

is using runtime_identifier