Originally posted by gerardbaron Import with the preview setting: embedded and sidecar
(1st import setting, top right on lightroom)
There are no sidecar files when using DNG raw files. The catalog contains your Develop adjustments unless you have the option selected to write changes to sidecar, in which case the adjustments are contained both in the Catalog and within the DNG file.
Two key points from Adobe's Help:
"Embedded & Sidecar - Display the largest possible preview available from the camera. This option may take longer than a Minimal preview but is still faster than rendering a standard-size preview."
"The Library module retains Embedded Previews until you edit them or you choose to generate other previews".
There is also a setting that directs LR to automatically replace Embedded previews with Standard Previews during idle time.
I suggest that the OP check the Apply During Import dialog to make sure that either no Preset or the desired Preset or Profile is applied during Import. I know that in my case one of the recent updates changed my default.