This is fairly common with the smaller,more modern probes--the old "clunky" ones didn't seem to do it as much.
I've found that some of these hook ends lose tension,& hence go open circuit,or as Psi said,it might be from a different set of probes.
If you get funny effects like this,ditch the "hook" & probe directly with the pinpoint end of the probe as a check.
After a while,checking for these effects becomes second nature,but you'll still get caught,sometimes.