Simply taking damage near the ender dragon allows its launch effect to take effect, even if the ender dragon is not responsible for the damage. This causes players to be knocked back by the ender dragon way more often, for instance, when the poison effect takes place.
Linked issues
relates to 3
Comments 6

Can confirm.

Thank you for your report!
However, this issue has been temporarily closed as Awaiting Response - this does not mean the report is not valid, we just need more information to verify it.
Please add the launcher log using these instructions to this ticket - please copy the log after the error has occurred.
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Here's the launcher log: https://paste.ubuntu.com/p/NHx3W3ZcHB/
Relates toΒ MC-105770.
Can confirm in 21w07a
Relates to MC-139286