The internal probe tip may have come loose and is causing the loss or intermittency of the signal. The probe tip might also be damaged. How to check: Pull off probe tip. Unscrew black insulation sleeve (item 2). Look at inner probe tip that is still on the probe.  You will see a metal barrel (item 4) with white or gray insulator at one end and a metal tip at the other end. Check that the inner probe tip (item 4) is screwed in tight.  Handling/rotating the outer probe retractable hook tip may have loosened the inner tip.  If loose: screw in finger tight.  (If needed, make sure future usage of the retractable hook tip does not unscrew inner tip by making it bit tighter.)  Reassemble probe and check the signal. If the problem persists, try replacing the tip with the extra cartridge included in your probe packaging (models TPP1000, TPP0500, TPP0500B). After replacing, attempt to perform a probe compensation. If this passes, then the problem is likely resolved. Otherwise, if the probe fails, then send in the probe for replacement. Note: The label on the inner tip could have shifted and now causing the tip to not fully tighten.  If the label is interfering with the inner tip screwing all the way in, reposition the label and screw finger tight the inner tip.  Then reassemble the probe can check the signal.