Issues with Descent depth gauge

G'day all

Went on a dive this morning, running my descent as my primary (as I have done for the last 30+ dives with no issues) and ol-reliable mares puck air as my backup.

Max planned depth was 22m and about 40mins of bottom time.

Long story short, around 12mins into the dive I got a warning from my descent that my Po2 was high and I should ascend or switch gasses, after consulting my backup my ndl was a little lower on the garmin but no more then 1-2mins, 30mins into the dive it happened again and the descent had gone from 20+mins to ndl down to 1min in the space of 30seconds.

Back on the boat and checking the max depth, it was at 219m!
@12 mins it had me bounce from 21m - 219m and then @31mins it went from 15m -210m.

Just wanted to throw this out there and see if anyone had the same issues?
To me, something like this could pose an extreme hazard, if the depth sensor was malfunctioning like it did but instead of taking me to a ridiculous depth and it showed me being higher then I was on a deeper dive you could easily slip into deco with out a backup computer.