I keep hundreds of gigs in sync between 4 computers and about 5 phones, including iOS (on iOS it’s Möbius).

It rarely has issues, when it does it notifies you of a sync conflict (it’s always a result of me doing something that’s bad practice, such as disabling sync for weeks on one device and making a bunch of changes).

Give it a try again. I especially recommend Syncthing-Fork for Android, it moves sync conditions into the individual sync jobs/folders. This enables me to have my DCIM folder sync to home, regardless of network or power conditions, so I never lose pictures, while allowing me to set my media sync folder (music, videos, etc from my home desktop) to only sync while on wifi, and other jobs to only run while connected to power and wifi.

Resilio is another great sync tool, works differently than Syncthing by using the bittorrent protocol. It has Sync-on-demand, which is great for grabbing media from my desktop from anywhere, Syncthing would only permit Syncthing the entire folder, with Resilio you can browse the share from your phone, pick files, and have it sync them right now.

I’d use Resilio more, just for that feature, but it kills memory on a phone because it keeps the sync database in ram when running, while Syncthing relies on files for indexing. So ST is my daily driver, and load up Resilio when I need to grab specific files.