It appears that the problem is related to the version string transmitted by Firefox Mobile. If they were to send an older user agent string, the issue would likely be resolved. However, any rollback would need to be implemented by Firefox, and it seems they are not at fault here.

From Google's standpoint, this issue may be considered a "new" bug, which means they need to conduct an investigation and address it. Consequently, a rollback is not a viable solution for them.