Spotted your thread earlier, but saw no merit in stating that I've had no problems. It's been several months since I last had reason to use the meter, so clamped my own tails a couple of hours ago (could have worded that better) and was relieved to read the sort of low leakage current expected.
I'm not sure there's much of use I can tell you - perhaps it's cheap for a reason or perhaps you and another person have just been unlucky, but I'd also noted the similarities between this and the DiLog version.
What I can state is that I've only ever used it to clamp tails and a cores on a couple of largish cables - I did make up a flex for testing leakage from individual appliances, but can't remember ever having use it.
Edit: Not sure if I posted a particular exercise in this thread or somewhere else, but I briefly owned a TEK775 (free with an MFT) and found results between the two were close enough to make no difference. The same was found when compared with a colleague's meter, which may or may not have been the Megger DCM305, and again recorded leakage was almost identical. Let's hope I haven't posted too soon!