Ridiculous Internal resistance reading

[Ikos]

About three months ago I have received 280 Ah cells for my setup and only now got to assembling them.
Back then the IR was, if I remember correctly, around 0.18 mohm, well below the manufacturer's stated value of 0.25. Now the measurement is 1.9-2.0 mohms. The voltage didn't change much, having dropped probably from 3.21 to 3.19 over 3 months rest.

How could that happen? Could IR really worsen that much? could the meter deteriorate?

Also I have discovered replacement probe needles in the meter's box and now I'm wondering what are they for? How do I know I need to replace them?

 

[sunshine_eggo]

Measured with?

 

[robbob2112]

The probe needles are for when you either A - do something foolish and burn the tips off, B - press to hard and break a tip off, or C - one falls out and you need to replace it.

 

[Ikos]

Measured with?

YR1030+

 

[sunshine_eggo]

YR1030+

Have you re-zeroed the meter?

Have you removed and reinserted the spring loaded inserts and cycled them in and out several times?

Did you scuff the battery terminals?