I had the exact same problem with an Envision 375 and tried all the advised remedies, new cut strip, new knife holder and oiling. After a few phone calls with our Midwest tech, I ended up replacing the whole carriage assembly.
When you take the cover off of the carriage assembly, move the plunger/knife holder (coil and magnet) up and down gently. It should move smoothly. If it sound/feels gritty, it may be time to replace.
I'm not saying this is your fate, however if it is, order the assembly from your Gerber rep/vendor and swap it yourself. If your handy that is...
It'll get you up and running faster than sending it in for service. You'll end up paying for a new assembly anyway, because factory service is gonna swap it out. It's quicker for the techs to swap it out with a new unit than to diagnose the old one. This is of course if the Envision is not under warranty or service contract.
I can't recall what it cost (I'll look at my records). It was pretty straight forward to swap out, not difficult in my opinion, and took about 40 min to do. The new unit comes with good instructions and a weighted balance for calibrating. The only PITA is seating the ribbon cables. But, I saved allot of time and the labor cost.