This is a challenging bug report.
I have been using After Effects since 1995 when it was owned by CoSa. I have never had a problem like this. Strange After Effects issue: Both of these movies used the same After Effects project file. The opacity fade didn't work in CC2018. After two hours of testing I rendered one last test in CC2018 (see attached file) and was not able to see the simple opacity fade. I then save the AE project file back one version to CC2017. I rendered the same test without changing a thing and was successfully able to get the simple fade to work. I am using a late 2013 Mac Pro with 32 gigs of RAM and OS 10.11.6
Any ideas on how to solve this issue would be approeciated.
Roei Tzoref commented
posting the project files would help
Anthony Venezia commented
Sorry about the typos.