Gravel block glitches in between two pistons when piston pushes it

In the beginning I added two pistons above each other with gravel blocks and Redstone. At first, they worked perfectly, then at the second I added four sticky pistons under the other four pistons and above them 3 gravel blocks. The pistons pushed gravel; however, the sticky pistons didn’t push pistons and gravel blocks glitched in between them.

it's Minecraft java edition