Lightroom Classic: Converts some Camera Profiles to Adobe Standard on raw import

Are you using the same in camera picture profile and settings. Is it possible you adjusted one of the in-camera settings (Sharpening, Color, etc.) for those "random" pictures. If so LR may be seeing them as assigned a custom camera profile and revert to Adobe Standard.

No, all Camera Profiles are "straight out of camera" with no modifications.

Hi Brian,

Can you share few more details for better understanding of the issue?

1) Does the problematic images have any sidecar .XMP files next to them?
2) If I understand correctly, images taken from same camera. Some of them are applied with camera matching profile but some are applied with Adobe Standard profile. If this is the case, can you please share two sample images: (1) Image where camera matching profile applied (2) Image (Problematic) where Adobe Standard profile applied. 

Thanks,
Ganesh

No sidecar files - just standalone RAW files
Dropbox 3 x files :
DNG28 was converted from Monochrome L Camera Profile into Adobe Standard on import
DNG29 & DNG30 retained their Camera Profiles on import
Dropbox folder - https://www.dropbox.com/sh/x2ivz07t9chc2f7/AABE_vHFxyuOAuKH_rmSlZvea?dl=0
other photos taken with monochrome L profile imported successfully
THANKS