During install twrp reads back -
"failed to mount /dev/block/platform/soc.0/f9824900.sdhci/by-name/userdata at /data :Device or resource busy
mount: failed to mount /dev/block/platform/soc.0/f9824900.sdhci/by-name/system at /system: Device or resource busy
script succeeded: result was [/system]"
Revise the installation script on: /yourrom.zip/META-INF/com/google/android/updater-script
Remove the mount instructions and mount them manually on the mount menu in recovery
During install twrp reads back - "failed to mount /dev/block/platform/soc.0/f9824900.sdhci/by-name/userdata at /data :Device or resource busy mount: failed to mount /dev/block/platform/soc.0/f9824900.sdhci/by-name/system at /system: Device or resource busy script succeeded: result was [/system]"
Will not boot. Error still in boot.img