problem in updating CM12 nightly on Moto G XT1033 I have installed CM12 Falcon nightly build on my Moto G 1st Generation XT1033 after installing CM12 I tried to update using Settings->About Phone->Cynogenmod updates first time it successfully installed CM updates but after that I am not able to install latest updates.

The system update is crashing in Recovery mode message saying
unable to install from zip

What should I do?

Note : I am using TWRP Recovery and not CM Recovery.
Here's a stopgap measure to keep your phone updated:

1) Nandroid backup. Necessary

2) Get latest CM12 falcon zip.

3) Copy zip to SD card.

4) Reboot to TWRP.

5) Wipe /cache and /system.

6) Dirty-flash ( common parlance for flashing without wiping userdata) the zip.

7) Cross your fingers and hope it works.

8) If it doesn't, there's your Nandroid backup. Now try a clean flash (in step 5, also wipe /data.

9) It should work (it's like installing a new ROM).

10) The next time onwards, download the OTA zip yourself, compare checksums of the files, copy the OTA zip to your SD card, flash the OTA zip without wiping anything.