WiringPI is going directly to the hardware, bypassing any knowledge of GPIO usage that the Linux kernel may have.
Most likely you have enabled something via config.txt that also thinks it is using GPIO4, and periodically it is checking it. Likely candidates would be a 1-wire interface as that defaults to GPIO4.
"sudo cat /sys/kernel/debug/pinctrl/pinctrl-handles may give you some more information on which driver has claimed the GPIO via Linux. Otherwise quote the whole of your config.txt (using code tags please).
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
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