The bug
Squids choose the direction they are simming in randomly. This means that they sometimes also try to swim "through" a wall. Whereas other mobs trying to walk against a solid wall just collide with it, squids sometimes glitch into it (maybe client-side only).
The reason
The following is based on a decompiled version of Minecraft 1.10 using MCP 9.30.
The reason might be that the class EntitySquid
is overriding the method net.minecraft.entity.EntityLivingBase.moveEntityWithHeading(float, float)
.
Linked issues
is duplicated by
relates to
Attachments
Comments


Confirmed for 17w17b & 17w18a

Confirmed for 1.13.1.

Confirmed in 1.15.2 and 20w21a.

confirmed in 1.16 pre-release 5

Confirmed for 1.16.4 pre-1

Affects 1.16.4.
Can confirm in 20w46a.
Can confirm in 21w03a. Also affects glow squids.
Can confirm in 21w05a.
Can confirm in 21w05b.
Can confirm in 21w06a.

In 21w11a

In 21w13a

21w14a

Confirmed for 21w15a

Affects 21w17a

In 21w18a

Can confirm for 1.17

Can confirm in 1.17.1.

Can confirm in 21w37a.

Still in 1.18 Pre-1

Affects 22w05a

Can confirm in 23w14a

Related to MC-208015

Affects 1.21.1
Fixed in 24w33a.
Can confirm for 1.11. Probably client-side only as you say.