Bubble Magus Dosing Pump

I am having an issue where my pump loses it's siphon and the stock solution drops back into the container. It loses siphon right at the intake pump head.

Anyone experience this issue? I am using 1/4 silicone tubing. Is that the wrong size? Do I need a special type of tube?

I am hoping that this is not normal.

I have read that people often install a one way check valve directly before the input to the pump head. That should help with any loss of siphon. Going to try this out.