it turned off for me

yeah I tried that too - absolutely nothing works, I tried a 'soft' reset, then full reset of all settings/data. they do not know how to fix it. and seemed to have no idea that this many people were having an issue 

I have been in a dialogue with Garmin Support and tried all their suggestions (factory reset, uploading watch files, account access, etc.) and even supplied a video of the watch misbehaving after I turn it back on to resume a run (it runs off as soon as I select Resume).

They have suggested a replacement but this would cost me over £90 which is too much. 

I firmly believe this is a software issue as so many of us are affected but there is no acknowledgement of that, nor a willingness to investigate it seems.

Hi,

I've been having the same issue for months now. At least once a month, during a run the screen randomly goes blank/off so every time I've stopped and held the on button in and it comes back on and my activity is there paused ready to be resumed. I resume it and carry on running and then realise it's added distance onto my run (usually just under 1km). It's so annoying. It doesn't do it on every run and I never go out for a run anymore without less than half the battery charged. I was wondering if it was to do with my watch getting cold but it's I've ran in colder temperatures and it's not happened then. It's happened again today which has brought me to this forum.

My watch is the forerunner 45S, bought in 2020, and the software is up to date - 5.4. 

1) I'm in the UK - North West region

2) you have permission to reach out to me

3) you have permission to access my account

Well, my Garmin 45 has just switched off yet again, and yet again at the two mile mark.  I've followed every suggestion on this thread and from Garmin themselves, who don't seem to have a clue and give every impression that they don't care.

I did.  They told me to a) switch the watch off then on again, and b) download the latest software.  I'd done both of those already.  They plainly have no idea what the problem is.

Same issue for me, turns off during a run at 60-80% battery. only minor difference is it seems like the shut down is triggered when I press the stop or back button.  Contacted support and after suggesting updating software and a reset they offered a out of warrantee replacement.  Posting here for visibility.

Same problem here. Garmin please do something !

This looks like planned obsolescence..

I am having this same problem. The 5.40 patch was applied to the watch a few weeks ago. Twice now the watch has turned off in the manner described, both times around mile 3. The watch is just over 3 years old. I no longer trust the watch and now concurrently run the watch and a phone app tracker. Seriously considering going to a different brand watch if I have to replace it.

Yes you can contact me.

Same thing has started happening to me, twice in the last two weeks watch quits at 60% battery in the middle of a run.  I restart it, it comes back on and quits again.  Usually on the 3rd try it will stay on for the duration of the run.  My forerunner 45 is 2.5 years old.  Has anyone had any feedback from Garmin or found a proper fix? 

Sounds like an aged battery to me. Increased internal resistance causes an excessive voltage drop under load (e.g. GPS), forcing the watch to shut down. On older Smartphones this happens all the time, especially in cold conditions. Unfortunately most new devices are sealed, so it's almost impossible to replace the battery. But if you do, the shutdowns are gone. If the memory was defective or this was an software issue, the watch would crash at any SoC.