Steps to reproduce:

1. Clean installation of Ibexa DXP 3.3
2. Create a landing page with 3 blocks inside, e.g. text blocks (textblock1, textblock2, textblock3)
3. Publish it
4. Edit the landing page again
5. Start dragging a block (e.g. textblock2) and then release the mouse button without changing the block position
6. Publish it or save the draft

Actual result:

The block has changed its order (e.g. for first or last position)

Expected result:

The block has kept its order

Note:
This behavior doesn't happen every time, but I've been able to reproduce it