Here's one that might stump you

[peterbaron]

That “ small hole” is called a compensating port and allows fluid to enter a brake line from reservoir.
Any restriction could mainly cause brake dragging ….. less likely spongy lever/pedal or more…

So, you're saying that if the compensating port was clogged and did not allow the proper amount of fluid to enter the brake line then this would cause dragging?

So, you're saying that if the compensating port was clogged and did not allow the proper amount of fluid to enter the brake line then this would cause dragging?
m in sc, just aswered your question : if its clogged it will just build pressure behind it and it drags.
.....due to the fluid expanding when the brakes are hot and instead of returning to the reservoir, it will push the brake piston out towards the pads and rotor, causing the brake binding.