Well ............. all good to know. I have no idea what the cause of my issues are.
My oldest track is 11/2016. I have been using the app for some time and never experienced issues with failure to sync. It cropped up on a trip to AZ early in October of this year. I noticed that my devices where not syncing.
Just before this I noticed that my iPhone app frequently crashed when recording a track. Very frustrating as one typically, at least I do, starts the track and ignores the app and lets it run in the background. What I discovered was that the app frequently crashed when taking photos with my phone. No warning or notice. It would just crash and when you reopened the app it would ask if you wanted to resume recording your track. Of course after some time had passed and you had a gap in your track.
I will point out that the taking of pictures was with the native iPhone app. Taking pictures within Gaia appears to not cause issues. Of course I really don't want my pictures ending up in the app plus it's inconvenient compared to the native photo app. I point out that this happened regardless of the number of apps I had open. I have repeatedly force closed via swiping up all apps except Gaia and the camera. No change I can tell in the frequency of the crashes.
That is when I started using an iPad as a backup to my iPhone track. It was here that I noticed that my app(s) were not syncing. Gaia support has stated that it appears was/is due to syncing routes that have a large number of points. I, however have synced lots of long routes, the entire Backcountry Discovery Routes library with no issues as an example. I have also synced long tracks, lots of maps, etc. without issues. Other than maps can take a long time to download but they show up across all my devices promptly.
I have had my iPad Pro open, high speed internet connection, and set to not sleep, for well over an hour with Gaia syncing without completing.
Gaia support has always responded promptly but they seem confused and at a loss. I am not sure if its good or bad news that others are not having this issue.
How many of you are using multiple devices to access your Gaia account? I frequently use the following,
iPhone 12 Pro - for obvious reasons
iPad Pro mainly for route planning and track reviewing while at home. Occasionally for track recording.
iPad Air as above, whichever one is not currently charging is typically the one that gets used.
iPad Mini is dedicated to my camper and is what I use whenever driving it. It is my most frequent backup to my iPhone track recording.