Used PISA pump vs brand new (following exclusive pumping with Symphony)- question about suction power/strength

I bought a used Medela PISA pump out of desperation when my son was on a nursing strike 4 months ago. I don't know the exact details of how long or often it was used but I know it was used for two children.

I currently EBF + solids, and we don't do bottles, but in about four to five months I have to return to work full time (my son will be a year old but I prefer to stick to giving him breastmilk instead of cows milk) and I have some concerns about the pump.

Last time I pumped was when my son started solids about two months ago (I wanted to add breastmilk to his oatmeal) and I barely got anything and it didn't feel like the suction was great despite the tubes/flanges/white membrane being in good shape (my own pumping kit from when I was pumping using the Medela symphony pump when my son was in the NICU).

When I pumped exclusively following my son's birth (for five weeks), I never got a lot (only 3-4oz and that was a MAX and only happened overnight at times) even using the Symphony.

Comparing the used PISA pump to the Symphony, the suction feels like it's not even remotely close in strength. I am worried that the suction at it's current power will not cut it when I have to start pumping at work.

I am wondering if when I go back to work I should invest in a new PISA pump but I'm hesitant to spend all that money if it is going to be similar to the used PISA which really seems mediocre to me.

Any suggestions? Does anyone have experience or could shed some insight on how much a pump's suction diminishes with time? Also if anyone that has pumped with both the Symphony and a new PISA could discuss their experience. TIA!