I thought the flashing only occurs when there is activity on the drive.
And there can be many types of activity done by a system than just reading and writing files to it. The files could be being indexed, the machine’s AV could be scanning it or checking it repeatedly for changes, etc. Why on one USB device and not the other? Different drive letters, different config settings, ie configed for Performance rather than Fast Removal, different drivers, different purposes for the lights, one indicates it is plugged in the other indicates activity, one indicates it is safe to remove the other indicates it is not, etc.
Check the drive letters and each device’s config. See if they are the same.
