Missing PDF display
After the October 2018 release update, if the PDF is opened with the output preview displayed, the display is frequently lost. This has not yet been resolved in update 2019.021.20056. Therefore, PDF checking in prepress is the reason why you should use 2017 instead of DC. I think that it was a problem that can be corrected because it was displayed normally before.
Thanks for reporting the issue.
Can you share a sample file with us for further investigation in which issue occurs.