SMART data reset by itself on WD Harddisk

I have a 1TB WD Green EARS from several years ago. It had 47530+ power-on hours. Last night I’ve noticed PC didn’t detect the disk. I’ve restarted the pc and it now had 0 power-on hours… It also reset everything else on smart report.

It also threw 63 read errors, 1038 power cycle and unsafe shutdown values. Apart from this weird, one-time incident, drive works flawlessly; good solid read curve in aida64, no surface errors, nothing to indicate drive is bad. It still counts all smart values properly, but adds to new values. It has 8 hours and 1 load cycle count on it now. Should I sell it? :smiley:

I dump smart values of my disks to an xls file on regular intervals, so here’s what its smart data was a month ago, its power-on hours graph from past 3 years, and its current smart status:

wd%20ears2b

This post is both a sort of bug report and a set of questions:
1- How did this happen? People trying hard to reset their smart data for fraud couldn’t even do it.
2- Is there a way to undo this? Be it manually, or via some kind of tool? I use smart status not only for errors, but to track the age of the drive; ie too much hours or load/unload cycles and I use it for less and less important data.
3- Should I dump the drive? It was my first reaction, but drive works as perfect as it did yesterday. I already use it for non-critical data due to its age.