Gillig LLC discovered that certain buses from 2013-2019 don't fully comply with a federal safety standard, specifically FMVSS No. 102, related to transmission safety. They reported this issue in 2019 and requested the National Highway Traffic Safety Administration (NHTSA) to consider the noncompliance as minor and not affecting vehicle safety. NHTSA agreed with Gillig's assessment, noting that the interlock system in these buses prevents unintended movement, and therefore granted Gillig's petition, exempting them from needing to notify owners or fix the buses. However, dealers can't sell the noncompliant buses without addressing the issue.
Simple Explanation
Gillig, a bus company, found out that some of their buses from 2013-2019 had a small problem with how their gear systems work, but this problem doesn't make them unsafe. The government agreed and said they don't have to fix or tell bus owners, but dealers can't sell these buses without fixing the issue.