[MCM-1258] Entities forgetting their functions after save and quit.

Partner Rank: 1
Partner Team Reporting: Spectral Studios
Verification Build: 1.16.40
Summary: Entities forgetting their functions after save and quit.
Impact: We are confirmed to be releasing our map on the 8th and this breaks our map experience fundamentally. Currently, when an entity spawns, our behavior pack gives them their brain. It tells them how to do everything and they go ahead and do it. But now when we save and quit then reload the map into the same map our dragons can no longer fly, and some of our custom mobs forget their attack functions. It's not that they've forgotten because they've been handed their brain when they spawn, it's that it's no longer firing. We've confirmed that they still remember their functions because, when manually executed, they trigger correctly. They just aren't being repeated.
Repro Steps:
1. Download and install world provided to Gregg in our partner chat
2. Load world and spawn any adult dragon (Clang, Nightstalker etc) /summon olcdf:clang
3. Fly it to confirm its flight functions are firing, (right-click entity, hold space to take off and fly around, use WASD and camera position to control flight)
4. Dismount entity, save & quit.
5. Load back into the same map
6. Mount the same dragon and repeat step 3.
7. Spawn a new entity to confirm that new entities remember their functions.
Repro Rate: 10/10
Observed Results: dragons are unable to fly after not retaining their functionality after save & quit
Expected Results: dragons should be able to retain their functionality after a player has saved and quit
Screenshots / Videos Attached: We cannot attach the video evidence so please use this google drive link -https://drive.google.com/file/d/1MVv_AaNAsleQNPFqBREJR9DgAC__Q3Go/view?usp=sharing [https://drive.google.com/file/d/1MVv_AaNAsleQNPFqBREJR9DgAC__Q3Go/view?usp=sharing
Regression Builds: This worked up until 1.16.40.
Notes: This involves a passed piece of content that is scheduled for release on the 8th of December. We have uploaded the world to our partner channel and pinged Gregg. Other custom mobs like the Mushblooms, Yeti, and Lava Golems also have this issue but they instead forget their attack functions.