My Time Machine fails to complete the initial backup - have tired 4 different external disks all firmware updated and PRAM zapped as well as SMC reset and still TM fails to complete

I wholeheartedly agree its an offending file out there.

Plan is total clean install of 10.14.1 and then validate TM, then using the SuperDuper more as a catalog than a source rebuild the apps from the App store, validate TM again, then the Apps from signed Devs not on the App store - validate TM and see what we have. The preponderance of my 'files and media' (90%) sit on iCloud with a DropBox back up, or my NAS and are not included in the TM image. Those that aren't I will revaluate why they really need to be local.

One good thing this is forcing me to do a selective clean up of the 'junk' I have carried over from my 2010 MB from upgrade to upgrade just dumped on this machine - nothing like riding Moores Law with the cost of SSD's to allow one to get 'messy'.

Console isn't giving me any hints so far and I think its just time to fish and not cut bait! Bite the bullet and go for a clean build out from scratch.

Yes there's more than enough time - using a new USB-C to USB-C external as the target TM was estimating about 3 hours to back up and the computer is running that process alone and off the network as well. Its transferring about 10-15M per second per iPulse and the application, right up to to when I went to bed. More perplexing is last night it shows that the 'in progress' file is already 941G when the target volume is only 647G, makes no sense at all!

it was JUST doing the TM function and the initial back up is about 600G however it seems to routinely fail around 350-400Gish. Appears to be going along just fine and then 'fails' and says that I might try again later and if I have repeated issues I should reformat the drive. The Activity Monitor isn't showing any unusual processes or run aways either. I have been a Mac user since 1985 (yes my first was the 512k 'Fat Mac' which I bought with the sale of my Apple II) this is the first time I have had any issue with TM. SuperDuper has no problem with cloning the drive so I am considering (oh the pain of this) wiping the drive and installing from a installer thumb then using Migration Asst on the cloned drive for the few things not in iCloud or my Apps store account. HOWVER I would rather solve this without the nuclear option if possible. I have done a zap pram and SMC reset (oh bring the start up chime back to the MBPwTBar please apple!)

I've used 4 different drives (Seagate, WD[new USB-C drive] and Toshiba) all reformatted as well several times here's the exact words I'm getting: "An error occurred while copying files. The problem may be temporary. If the problem persists, use Disk Utility to repair your backup disk."

I've used a variety of tools to validate all 4 of the drives and the firmware on the drives themselves.

They work fine with 3 other Macs I have from the new 2018 MBA to a 2012 i7 MM as well as 2 other MBPs (2012 and 2017) so I'm assuming this is a unique issue with this hardware.

However I am open to anything Grant.

what's really even more interesting is the TM says its only backed up 500ish Gigs of the target 650G and yet the ** file on the external is over 900G already

Thanks for the reference I am going to delve into it. As I have a clean? SuperDuper clone I am considering the nuclear option now - go ahead and blow this MBP away do a clean install and see if that can be backed up before I do any builds on it - the marginalization of hunting this bug out into the open is taking more time than to reset the table entirely <grin!>

Any thoughts other than the above to my approach?