Here is a decent write about about 4 such student lawsuits...funny you mention the federal government, because as you will see in this article the Dept. Of Ed. Was involved in these efforts to reset the discharge clocks, because the program was going to cost them more than expected. Specifically right before the first batch of discharged loans the Dept of Ed changed their rules on the fly (in violation of the Act) to make students ineligible for discharge.

https://www.studentloanplanner.com/pslf-lawsuit/

Edit: I think In all 4 of these cases the Dept. Of Ed. Already approved these discharges, sent approval letters, then changed their rules and revoked the discharges. Again the rule changes were in violation of law and done because the costs of the program were so large.