Got the mastech recently, works well enough, and does not have the drift as bad as yours, and the switch has good end stops. Does work well enough with the little work I have done with it, and measures easily down to under 100mA DC. Seems to be at least usable, and I did want DC current and TRMS in my next meter, this came in cheap and probably good enough.
Will have to read the manual and print it ( came with the Chinese version, but got a download of the engrish one) later. Did not even realise the torch in front of jaws, nice addition, did not notice it.
I think inrush test will be to take to work and check on the battery cable of the van during start, should do the trick. Can check the alternator as well, and see which connection is actually doing the bulk of the work, the original wiring ( cheap spade connectors that died and went intermittent after 10 years of use ) or the new short thick 4mm cable bolted at both ends to get good contact.