poplar is fairly soft also. Your first thought may be the cure for that one. I think Hal may have answered your tape question on the tracking issue, but if the machine is telling you front roller stuck thats something else.
If you do a search for (roller stuck" ) you will find some posts about it an how to fix it.
I just had that on one of mine. Basically remove keypad side cover (careful to not damage wires), remove the two screws holding the roller in question in, drop it down and blow it out and a hairball should come out. then put it together and carve.
Brent
A,B machines, PE,probe,conforming vectors, centerline, 2d,3d,stl and dfx imprt, rotary , 3.xx, Pattern Sculptor
OS X Yosemite
Woodwork is what I do to pay for my tool addiction.