PDF colour display/rendering issues Acrobat Reader DC

For approx. the last couple of months in my office we have been having issues with the display of most of our PDF drawings in Acrobat Reader DC (currently running version 2019.008.20081). The drawings were produced in AutoCAD LT. The issue is affecting not only new drawings produced but also historical files, so we are certain that the issue lies with Acrobat - it is also affecting all PC's in the office. As you can see from the attached image the issue is such that we are having to use other pdf viewers - it shows the same file opened in Chrome (left) and Acrobat Reader DC (right).

Changing the preferences smoothing lines, fonts, pictures has no effect.

Is this a known issue - if so is there a current fix or will it be resolved in a later version? The workaround we currently have for clients in producing the PDF's is not going to be viable long-term, and I imagine displaying PDF's produced in AutoCAD is a fairly common scenario.

Many thanks

Rachel