Nexus 6 - Can't boot TWRP recovery

I was trying to fix an issue with my phone the other day, and saw that re-locking the bootloader might fix it. Nobody mentioned anything about it completely wiping the phone, including the internal SD card. I set most of the stuff back up again but realized that it was suffering from the bug on the old radio version that causes it to lose LTE randomly.

I went and rebooted into TWRP to try and flash it, and TWRP showed a completely empty sdcard partition and said it could not mount '/data'. I enabled "require pattern to boot," thinking it may not have known to decrypt the partition without that, and now I can't get into TWRP at all. I tried disabling the "require pattern to boot" option again but no luck. It shows the "Google" logo for about 5 seconds, then the blue "TEAMWIN" logo for about 3 seconds, then reboots to the "Google" logo and proceeds to boot normally. I should note that I have CM12.1 installed, and the latest TWRP. I've tried reflashing TWRP and that didn't help; I also did "fastboot format cache" and then "fastboot flash cache cache.img" using the stock factory cache.img. I got the radio flashed using fastboot, but I'd really like to have a working recovery.