Summary:
Crawl mode is activated when you sneak and jump onto the bed. If there is a block above you at the moment of jumping, you will be completely crawling, otherwise you will be crawling for a moment, and then you will be pushed out by the blocks. In versions 1.20.73 and below the player starts crawling without jumping - see MCPE-178370.
Steps to reproduce:
Place the bed.
Place a full block 1 block above the bed and you.
Sneak.
Walk close to the bed and jump.
Observed results:
The player starts to crawl when jumping.
Expected results:
The player does not start crawling when jumping.
Video:
[media]Linked issues
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Comments 6

Can confirm. If there is a block above you, you will go completely crawling, just like MCPE-178370.
This has been fixed in 1.21.10.22 according to Minecraft Beta & Preview - 1.21.10.22 – Minecraft Feedback.
@unknown: Yes, we know. This was reported in a 1.21.0 Preview and wasn't fixed until 1.21.10 Preview so it'll still be in 1.21.0 when it's released. This will be updated at the appropriate time.
@Auldrick, I wasn’t exactly sure of the update procedure that Mojang uses. Thanks for clarifying!
Reply from @unknown:
To request action on a bug report, you may want to join the Mojira Discord. This is both more reliable and reduces clutter on the bug tracker.