Troubles with Digital Vacuum guage

[cal2e]

I have a SVG2, Digital Vacuum Gauge that I hook up inline with my R410a guages and i have a T piece that goes down to a tap inline also that once i have vacuumed down and it holds i can switch tap off so when i charge the hoses it doesn't affect my digi vac..

My problem is the first 10 or so times i used it, it held perfect ( as in i vaccumed down and switched off and the guage only creeped a little then flashed stable..)
now though i can vac down then when i switch off it will NOT hold.. i thought it may be my hoses but i try everything and still does't hold..

do i need to calibrate the digi vac over time..?
i tried cleaning sensor with acohol to see if that would work and it still does this..

everyone i have asked said im wasting my time using one..

but it use to work fine..
just would like some advice

[Brian_UK]

Are all of the seals in good order? any tubing leaking due to old age? valve seals leaking? all things to consider before condemning your gauge.

[monkey spanners]

Moisture or leaks, i've found the little rubber gauge line gaskets to be a common culprit, even if the look ok.

Failing this, can you borrow another gauge to compare it to?

[Tesla]

You could check the vac stat by directly connecting to the vac pump - with new oil you should expect to get around 25 microns if the pump is any good.