This rom comes pre installed with dual recovery, TWRP v2.6.3.0 and philz touch 6.0.4.5. I am not sure about the theory that upgrading to 2.7 will fix anything because the flashing process will be the same after which apparently a boot loop will result if the partition is encrypted. In general users with encrypted partitions should be careful with modified roms because they are mostly targeted for unaltered partitions.I got my stock 4.4.4 rooted, but unfortunately not with this ROM. Below are my thoughts on what the problem may be.
system.flashable.zip only includes TWRP 2.6.*, which apparently has issues mounting encrypted partitions. These issues are solved in TWRP 2.7; can the OP update system.flashable.zip to include 2.7?
For those who still want to use this ROM, after flashing system.flashable.zip, I'd immediately install dual recovery before rebooting. I've not tested it myself but it's my theory for what will work.
Unfortunately the only solution I can only think of is to turn the tablet off, turn it on in flash mode and use sony mobile companion or sony update service on a PC to restore it to an unmodified OS. This will obviously erase all data.