After a paper jam which I cleared as directed, the machine now runs all the time on the ready position and will not stop after paper has been shredded.

SOURCE: Shredder stops in the middle of shredding and won't shred.

I have the same problem with my shredder. I opened it up and found one of the gearwheels had teeth missing. That is why the partial shredding could not advance further. I was able to remove the part and am now hunting for a replacement.

SOURCE: Powershred 380-c

Possible door switch or the bag full plate under the machine jamed ot switch bad. Also All shredders need the wheels oiled with shredder oil now and then...

SOURCE: the shredder will run in reverse but will not run foreward.

Inside the shredder there is a motor which is wired to run both forward and backward, the way it does this is to transfer the power from the switch to a couple of wires on the motor
The forward running motor will be linked to the auto start button which will tell it to work with the paper sensor.
When you select the Forward function the Auto Start is taken out of circuit and the Forward switch should supply the motor

After all of that I would say that the switch is open circuit on the Forward contact and needs replacing

SOURCE: staples spl-710sh paper shredder stopped shredding

This exact thing has happened to my unit as well. Ive disassembled it to discover that 5-7 teeth on the gear that the motor drives have been stripped off. Unless the gear can be replaced (which is probably not worth the expense), then the unit is toast. Sorry. Good luck.