Makerbot replicator 5th Generation: Extruder Issue

Hi thank you for taking a minute to help us out with an issue.
Our school tech lab has 2 Makerbot replicator 5th Generations and 2 Makerbot replicator 5th Generation Minis.

Over the past few months the display screen has been stopping prints and projecting that the extruder is jammed and must be reloaded, or that the extruder is entirely not connected to the printer. Neither of which is true. These extruders are also not holding their temperature once reached. We have tried to replace a few of the extruders with the same make and model stock extruder, but the new ones gave the same results.

Any leads as to how to solve this problem will be greatly appreciated. If a solution cannot be reached, redirection to another source would also be wonderful.

Thanks
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