I've been using RTM on Apple Watch, but the sync is painfully slow.

This has always been a problem. It seems like I have to leave RTM open on the Apple Watch for 3 to 4 minutes for it to actually sync.

I'm on the most recent version of iOS, and I'm on the latest version of RTM. I have an Apple Watch Series 2 and an iPhone 8 Plus.

The RTM app for iPhone is working great, syncing fast... no issues at all.

I tried the usual steps... restart devices. Re-sync. Uninstall/reinstall from Apple Watch. Uninstall/reinstall from iPhone.

I went so far as to factory reset the iPhone and the Apple Watch and install and sync from scratch. The problem persists.