I can attest to the efficacy of the method described on pages 17/18 by Picinic and others. After more than a year of wrangling with the "zombie shortcuts" problem I had collected and attempted several different solutions. To those who are considering using different methods such as signing in/out of iCloud, turning dictation on/off, applying the various terminal commands, etc., I can assure you of this: They will NOT work long-term.
For some reason I had viewed the difficulty level of implementing this solution as moderately high and avoided it. That was a mistake as it turned out to be incredibly simple, relatively fast and, after about a week of watching and waiting, effective.
To be clear, I have tried EVERY solution. This is the only one that works. And it is far more simple than you might think.
A few notes for those reluctant to dive in:
- While I'm sure that the recommended application in this approach will work I found that I already owned an application (iMazing, which I highly recommend) had access to the same backup file structure. The interface is excellent and finding the necessary files/folder to delete was simple. I know nothing about iBackupBot/iCopyBot and can't comment on those but can state unequivocally that iMazing is an excellent tool.
- Restoring the phone from the modified backup was far less painful than I had anticipated. I've done full restores before and expected to have to go through a lot of nuisance factors to restore it - especially not knowing anything about this method - but it turned out to be about a one-hour process for my iPhone 6/64GB with about 120 apps, 7500 songs and 10,000 photos. YMMV but it was pretty quick for me. Note that I did this via a USB/Lightning cable connected to the computer and not wifi.
- After the full restoration the phone did require me to enter the password for my Apple ID and iCloud but that was all it took. It appeared to me that some things were missing at first glance, in particular my credit cards in ApplePay, but rather than starting to reenter things I decided to wait it out and see if iCloud synced everything. After a few hours absolutely everything came back. Be patient and don't touch anything after the complete restore. It will all come back eventually depending on your contents, phone model, computer, etc.
After following the remainder of the instructions including those to go through all of the shortcuts on each device and clear out the ones (for the umpteenth time) that I wanted to delete, I can report after about five days that the zombies are gone and the syncing of new or modified shortcuts is immediate and flawless.
In short, stop kidding yourself and screwing around with other methods. I avoided using this method because I had convinced myself that it would be difficult. It was not. At all. If you are suffering from the zombie shortcuts problem stop what you're doing, devote an hour or so to this solution and it will be fixed.
My heartfelt thanks to all of the people in this forum who have taken so much of their time to develop a solution that solved an incredibly annoying and productivity-killing problem for me. This is part of what makes the Apple community terrific and I am sincerely appreciative of their time, research, experimentation and careful documentation.