[Moto G4 Plus Guides, News, & Discussion] HeethJain21:
If you run the ls -l /persist command on android P ROM (which is causing this IMEI issue), this is the output you get:

athene:/ # ls -l /persist
total 88
drwxrwx--- 2 system system 4096 1970-01-10 08:37 alarm
drwxr-xr-x 2 vendor_mot_pwric vendor_mot_pwric 4096 1970-01-01 01:01 batt_health
drwxrwx--- 2 bluetooth bluetooth 4096 2018-03-29 00:04 bluetooth
drwxr-xr-x 2 vendor_mot_tcmd bluetooth 4096 1970-01-01 01:01 bt
drwxr-xr-x 4 vendor_mot_tcmd vendor_mot_tcmd 4096 2018-03-29 00:04 camera
drwxr-xr-x 2 root root 4096 2018-03-29 00:04 coresight
drwx------ 5 system system 4096 2018-03-29 00:04 data
drwxrwx--- 2 system graphics 4096 1970-01-01 01:01 display
drwxrwx--- 2 system system 4096 1970-01-01 01:01 drm
drwxr-xr-x 4 vendor_mot_tcmd vendor_mot_tcmd 4096 2018-03-29 00:04 factory
[COLOR="red"]drwxrwx--- 3 vendor_rfs vendor_rfs_shared 4096 2018-03-29 00:04 hlos_rfs[/COLOR]
drwxrwx--- 2 root root 4096 2018-03-29 00:04 lost+found
drwxrwx--- 2 radio radio 4096 2018-03-29 00:04 mdm
drwxrwx--- 3 system system 4096 2018-03-29 00:04 misc
drwxrwx--- 2 system system 4096 1970-05-31 18:25 properties
drwxr-xr-x 8 vendor_mot_tcmd vendor_mot_tcmd 4096 2018-03-29 00:04 public
[COLOR="Red"]drwx------ 6 vendor_rfs vendor_rfs 4096 2018-03-29 00:04 rfs[/COLOR]
drwxrws--- 2 vendor_mot_tpapi vendor_mot_tpapi 4096 2018-03-29 00:04 security
drwxrwxr-x 2 system system 4096 2018-03-29 00:04 sensors
drwxrwx--- 2 system system 4096 2018-03-29 00:04 time
drwxr-xr-x 2 vendor_mot_tcmd vendor_mot_tcmd 4096 1970-01-01 01:01 wifi
drwxrwxr-x 2 vendor_mot_drm vendor_mot_drm 4096 1970-01-01 01:01 wmdrm

Notice how, android Pie is using

vendor

suffix prefix.

One fix that was thought was to fix the owners in android Pie ROM itself before flashing Stock ROM, but on rebooting, the owners were changed back to vendor_rfs and vendor_rfs_shared.

Also, if you flash an Oreo ROM after flashing Pie ROM (which broke IMEI), this is the output you get:

athene_f:/ # ls -l /persist
total 176
drwxrwx--- 2 system system 4096 2018-10-21 07:40 alarm
drwxr-xr-x 2 mot_pwric mot_pwric 4096 1969-12-31 19:02 batt_health
drwxrwx--- 2 bluetooth bluetooth 4096 2017-01-12 03:35 bluetooth
drwxr-xr-x 2 mot_tcmd bluetooth 4096 1969-12-31 19:02 bt
drwxr-xr-x 4 mot_tcmd mot_tcmd 4096 1969-12-31 19:02 camera
drwxr-xr-x 2 root root 4096 2016-07-31 00:43 coresight
drwx------ 5 system system 4096 2017-01-12 05:21 data
drwxrwx--- 2 system graphics 4096 1969-12-31 19:02 display
drwxrwx--- 2 system system 4096 1969-12-31 19:02 drm
drwxr-xr-x 4 mot_tcmd mot_tcmd 4096 1970-01-01 06:48 factory
[COLOR="red"]drwxrwx--- 3 root root 4096 2018-03-29 00:04 hlos_rfs[/COLOR]
drwx------ 2 root root 4096 1969-12-31 19:00 lost+found
drwxrwx--- 2 radio radio 4096 2016-08-04 20:26 mdm
drwxrwx--- 3 system system 4096 2017-11-09 16:30 misc
drwxrwx--- 2 system system 4096 1970-02-11 17:39 properties
drwxr-xr-x 8 mot_tcmd mot_tcmd 4096 1969-12-31 19:02 public
[COLOR="red"]drwx------ 6 root root 4096 2018-03-29 00:04 rfs[/COLOR]
drwxrws--- 2 mot_tpapi mot_tpapi 4096 2016-11-17 16:38 security
drwxrwxr-x 2 system system 4096 2016-07-31 00:43 sensors
drwxrwx--- 2 system system 4096 2018-09-10 18:13 time
drwxr-xr-x 2 mot_tcmd mot_tcmd 4096 1969-12-31 19:02 wifi
drwxrwxr-x 2 mot_drm mot_drm 4096 1969-12-31 19:02 wmdrm
athene_f:/ #

Here are some of the points that can throw some light on the topic: