New Plasmacutter

Oh, that is missed position due to steppers loosing steps, or the torch touching the plate and motors skipping due to friction/load.
Also can be due to interference, so move the plasma source as far as possible from the PC and electronics, torch cable also far from other stuff, best hanging from the ceiling.

Plasma is a "brute force" type of machine, so not for small or intricate designs, still a lot can be done with it.
What nozzle are you using?
Why 25A ?
-Set it at 40A and try it faster, see how that goes.
-Also, change the nozzle, set the pierce height to 3 or 4mm and test if it fires consistently, try different speeds...
-25A is not good as the nozzle has to be very close to the material
-Nozzle will have to be changed anytime the material flexes when probing and the torch fires very close or touching the material
-use 1mm or 1.1mm nozzle for 2-3mm @ 40A, 1.3mm or 1.4mm for 4-6mm @ 50A

Yup, those seem to optimistic for a 30A plasma cutting machine using plain air.