Same issue happened for an out-the-box-brand-new printer.
I found the "Marlin Ver. 1.0.1 - 2020/04/25" online downloaded and installed in the printer - Issue is gone, but I want to confirm I should have another version!

ALSO: I'm concerned about double temperatures when using OctoPrint (see: https://community.octoprint.org/t/octoprint-doesnt-show-a-temperature-graph-for-my-creality-printer/23901#double) - Do we have a fix for that yet?

Thank you!