when you pump the pedal does it start getting really solid?

If so more than likely you've just got some air in your lines and could use a bleed job.
with my experence with master cylinders once they go its the same problem constently not sometimes here or there.
I would think your safe, also you might want to check the brake lines where they go into the caliper "rubber hoses" for cracks also wetness on the hose or on the caliper

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