4mm contacts. I have a bunch of them. Some were very unsteady and read fluctuating readings. Esp on small hobby packs. Switch cleaner not doing the trick.
So I ordered a 4mm wire brush. Total transformation. Those 4mm connectors on the PL8 get dirty!
Like this one.
https://www.ebay.co.uk/itm/145472812214
Should you have a simlar issue reading resistance or fluctuating readings. Easy fix. Quick squirt of switch cleaner and hit it with the brush! Graphs are all dead smooth and precise again.