PLEASE HELP ME CONFIRM:
for those that are rooted on their LGV20, please check /persist/rct.cfg and see if it mentions a modified system with a modified /system partition. also from a shell, do a 'ps | grep sh' noting if there are numerous 'sh' processes. if there are then do a 'ps | grep rctd' and see if the PPid of those numerous processes match the PID of rctd. I'm willing to bet they do for most of them. the longer your device has not been rebooted, the more of these 'sh' processes you should have. please report back!
EDIT1: thanks to all those in this thread that helped put this nagging nail in the coffin! long story short, rctd is LG's root checker and it's started as a service within init.lge.rc, which is part of the boot/ramdisk so commenting out the lines that start the service need to be done in the boot.img itself. As a result for those that use stock kernels, I've created boot.img for 10k and 10p on the H918 T-Mobile variant of the LGV20 and 10h for the US996 unlocked variant of the LGV20.
H918 10k MD5SUM: 55a8dfd66ec9444a4a0d67eb39b34551
H918 10p MD5SUM: 9aa4cd481f1177f9d9d9f833f166ce80
US996 10h MD5SUM: 2bec2db396a81c73916ee3726e4cd334
flash your correct boot image and then remember to flash Magisk or SuperSU immediately after BEFORE LEAVING TWRP especially for those on 10k or 10p!!