Flashing the 4.3 factory image downgrades everything. For what it's worth, I noticed that the userdata partition is constructed differently than in 4.2.2(my last factory flash). That could have something to do with it. But also, I've been on custom ROMs since I got the tablet, yet I've never rebooted on 4.4.X. I guess try a vanillish ROM(like RastaKat) to see if that reboots.
Phone: Google Nexus 5 "hammerhead" ROM: LiquidSmooth F2FS Kernel: ElementalX 1.00
Tablet: Amazon Kindle Fire (Gen 1) "otterx" ROM: CM11-F2FS by Hashcode
Tablet: Google Nexus 10 "manta" ROM: LiquidSmooth F2FS-All Kernel: KT-Manta F2FS-All
Retired: Sprint Motorola Photon 4G "sunfire", Sprint LG G2 "LS980"