Descent MK2i T1

I bought the Mk2i and T1 before covid and didn't use it for a few years. On my first dive I noticed a 30 bar difference between my Descent and SPG. I put this down to my lack of knowledge of the watch settings, but went home and read EVERYTHING about the device, however I also contacted Garmin who were quick to let me know that the warranty period had already expired!

I updated software on both the descent and T1 and changed some settings. On my next dive I was so disappointed to see that the problem STILL exists so I took it to my local dive shop who replaced the transmitter battery. Upon testing there is STILL a 30 bar lower reading. 

am sick and tired of this very expensive top of the line device which is now out of warranty despite I only used it 2 times (but the data was useless). I have contacted Garmin again but I'm.still.waitimg for a response.

How many people have to complain, or potentially die before Garmin helps. Thank god we all have back up SPG as this is utterly useless.

GARMIN PLEASE HELP ME.