Step count dropping overnight

I am seeing similar complaints at Vivo devices relatively often, here on the forum, so there is probably indeed some problem in the way they sync the data to the server. I recommend verifying always before midnight whether the full count synced to your Garmin Connect account. Please note, that the Steps panel on the My Day screen of the app does only show the step count synced from the watch to the app, but is often not the same count that was already synced to the account on Garmin's servers! To see what was synced to the server, you have to tap on the Steps panel, and verify the number on the detailed screen. Alternatively you can check the steps count in Garmin Connect Web.

When you see a lower number on the detailed Steps screen (or in GC Web), then repeat the syncing again, forcing so the app to push the data to the server. Repeat again, if necessary. Once the count is on the server, it should be safe.

Did you resolve this?

What does the step graph look like? Do you see a drop or from at what time is the final step value taken?

No unfortunately not. I synced about 20 times last night and couldn't get the daily summary to match the step count on the step graph.

Yeh so my daily summary and watch match but when I click on the steps, that is less sometimes it's a very significant difference, I was down 1k steps last night, the continual syncs helped Abit but didn't resolve it completely. 

At the moment daily & watch = 3200 but steps graph = 31790 not a huge difference but adds up over the day. 

I have been having same issue.  I found that my website profile had a different time zone than my phone.  Since I changed the website time zone to match the phone the app seems to be updating steps correctly.