Have had my Garmin Vector 3 for about 3 months. In the last few weeks have had nothing but problems. When riding Cadence drops out every few minutes and power spikes. Have taken batteries out and cleaned them and contacts. Same problem. I have the new battery caps.
So after searching around the internet I found the usual add baby oil to battery surface and rear. Add baby oil to contacts. I used ear bud.
But I also read and applied the following. Cut small strip of electrical tape and wrap battery's so they wont move. Thin tape and only overlap tape by 5mm.
I have now ridden 3 rides of approx 1hr each and have had no problems. Garmin Edge 1030 and Zwift now work spot on. No dropouts and no Power spikes.
Will Update over the next month. If you try this and have success also please leave reply here so other users can see if it will work for them.
And Garmin why don't you fix the problem. I should not have to spend over $1000 on pedals that I have to apply electrical tape and baby oil.