Proximity card reader intermittently flashing amber. Will not register card swipe.

[PrinceOfPrints]

In our organization, we have 12 HP printers configured with proximity card readers to facilitate secure pull printing. Recently, two HP Color LaserJet FlowMFP M681 printers had their firmware updated to version 4.9.0.1. This update may not have been the cause of the change in behavior, but recently both of these printers started having their proximity card readers fail. I've yet to find a pattern, but almost daily each will have its card reader stop registering swipes for Secure Pull printing (the secure pull components remain installed on the printer). 

I want to try to rollback the firmware version, but don't see a download from the printers' software page at support.HP.com. Can someone suggest where I might find older firmware versions for this model printer? 

Of course, if someone can suggest another fix for the proximity card reader problem, I welcome any.

[PrinceOfPrints · Accepted solution]

Based on the HPAC admin' guide, I turned "Auto Off After Sleep" to off:

NOTE: When devices with FS4 Firmware go into deep sleep (1-watt sleep mode), power is turned ot to the USB ports. There is a chance the USB ports (and card readers) will not reconnect when power is back on. Devices with FS4 firmware include an option in the device EWS > General tab > Energy Settings > Sleep Settings for "Auto Ot After Sleep". It is recommended that this option be disabled on any device that has a USB card reader attached, in order to prevent them from trying to go into deep sleep (1-watt mode).