As stated above, could definitely be your bass. Best way to troubleshoot is to separate components and test them: bass, amp, and cab.
Try a different bass with your rig. Same problem? Then not your bass. Try a different cab. Same problem? Not your cab. Etc.
Try your bass at a local music store and see if it happens there - if you don’t have a second rig to test it through.
Lowering your pickup is as easy as carefully turning a screwdriver. (Push down on the pickup while turning screwdriver - this takes tension off the screw’s threads and lessens the likeliness of stripping the screw head with too much force.)
Try a different bass with your rig. Same problem? Then not your bass. Try a different cab. Same problem? Not your cab. Etc.
Try your bass at a local music store and see if it happens there - if you don’t have a second rig to test it through.
Lowering your pickup is as easy as carefully turning a screwdriver. (Push down on the pickup while turning screwdriver - this takes tension off the screw’s threads and lessens the likeliness of stripping the screw head with too much force.)