Disappearing strokes after pathfinder crop

[#1]

Hi. Im trying to make seamless patterns and want to crop the 3x3in design ive created. But when i select the pathfinder crop option (after masking the design), I find that all the stroke line (without fill) are disappearing. How do i solve this?

Thank you

[#2 · Accepted solution]

Pathfinders and strokes don't go together well.

Outlining strokes before applying the pathfinder would be an option.