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: Sprint LG G2 "LS980" ROM: LiquidSmooth 4.4.2 Kernel: Varies
Tablet: Amazon Kindle Fire (Gen 1) "otter" ROM: PAC-ROM 4.4.2
Tablet: Google Nexus 10 "manta" ROM: Purity 4.4.2 Kernel: KTManta
Retired: Motorola Photon 4G.......Never again Motorola.....