So I have a few theories. I have now had 3 different USB sticks fail on me: Two Sandisk 4GB SDCZ33 and one cheap generic 8GB replacement.
The power draw of the TP-Link system + USB is probably more than the opportunistic USB ports they get plugged in to. An underpowered probe runs great MOST of the time, but a flash bit write is probably the highest power strain and Flash can get really unhappy with power interrupts, based on this SSD research:
https://www.usenix.org/system/files/conference/fast13/fast13-final80.pdfI usually use a 500mA or 800mA supply, or tap a nearby router USB port in that range.
I suspect the system may demand 1200mA or more.
When most flash sticks get errored out enough, they permanently fail into a read only mode, or become fully unreadable. Read-only mode can be reset on some models, but it is not recommended by the vendor. At least one of the failed SANdisk units I had was stuck in a read-only mode.
Also, probes may be subjected to ungraceful power down situations, depending on where they are stationed. That can also be a flash drive killer.
I don't think we are hitting the write limits of the sticks. I suspect the units are often in underpowered or ungraceful pwoer-down situations, or the USB flash itself is not responding gracefully to poweroff situations.