Bruji

Every time I try to sync Bookpedia to my Pocketpedia, even if I've only added a handful of changes, all 8600+ covers re-sync. I recently got a new phone, but it's the same model as my previous one, with just more memory. I'm in the middle of my third full sync in two days. Help!

It sounds like it may not be completely finishing the sync. So because you have such a large data base try the following

1 - Go into the relevant macOS pedia, hold down the Option key and from the Help menu choose 'Export for Pocketpedia' and export the resulting file to Desktop. (this creates a file with all the covers and info that you can then sync via macOS Finder) [It's quite large as it contains all the covers regardless if Pocketpedia already has them]
2 - Connect your iDevice via cable to your Mac
3 - Open Finder and select your iDevice on the left under Locations
4 - Let all the automatic Sync'ing and Backup processes complete
5 - Click on the Files tab in Finder iDevice window. Pocketpedia should be listed here
6 - Click on the Pocketpedia entry drop arrow
7 - IF there is an entry with or without data in it - Delete by right clicking
8 - Drag the newly exported file from the Desktop onto the Pocketpedia Files section and Drop it on top of the Pocketpedia entry to import
9 - When it has finished copying the file, (which may take some time - spinning Beachball) run Pocketpedia to have it import the file and all the covers.