Well after 14 years it had to finally happen.
Never seen or wanted too see this message pop up.
And checking syslog sure enough I can see multiple instances of the below so I guess my flash drive is toast.
Apr 3 19:35:21 unRAID kernel: critical target error, dev sda, sector 18618 op 0x1:(WRITE) flags 0x0 phys_seg 1 prio class 2
Apr 3 19:35:21 unRAID kernel: Buffer I/O error on dev sda1, logical block 16570, lost async page write
Its still hanging in there but with all the write errors its pretty much a goner.
At least unRAID has given me fair warning.
New Samsung BAR plus on the way to replace the crappy SanDisk UltraFit 🥺