leakage clamp meter accuracy

[Sadsyndrome]

hello.
I'm using leakage clamp meter to investigate nuisance tripping in my house. It is a MULTICOMP PRO MP780050 that I bought early 2021. However, once I bought it the nuisance tripping stopped, so I put it down to damp in garage at the time. This looks just like the Dilog6518 (just without dilog badge).
house is mid 1980s with wylex board 6 off mcbs with 30ma RCD protecting them all.

2 years later...
Grill has tripped rcd a couple of times in recent weeks (including last night). So I thought I'd use clamp meter to investigate, clamping meter over L-N meter tails dangling meter vertically.

results were:
10mA leakage initially
with kettle 48mA!
with kettle and grill 114mA!!

30mA RCD didn't trip in the test? It did trip when I pressed RCD test button.

q1
How accurate are these clamp meters? am I correct in letting meter dangle vertically from tails, as holding meter horizontally did seem to change reading significantly, also clamping main earthing conductor gave significantly lower reading.

q2
what is approximate, normal baseline leakage in house with no heating elements in circuit (e.g. fridge, CH, TV, broadband router, led lights etc.)?

q3
why didn't rcd trip during my test. even assuming meter readings weren't accurate 114mA does seem very high.

q4
any ideas how I can roughly assess meter accuracy? I guess warranty is expired now

I was going to replace board to Hagar with rcbo per circuit. I think I need to get to bottom of this issue first though.

thanks

 

[newfutile]

I would guess the meter has a problem ,to assess its accuracy you could make a lighting circuit ( pendant on a plug with live and neutral wires separated from cpc)
insert a lamp and measure , it should read 0, set the meter to read maximum and hold and use (RCD) Residual Current Device tester or mft to set various currents, the clamp meter should read similar to the test current (within reason)