I’ve attempted reproducing this in the latest 4.12 Preview but haven’t had any luck doing so. I tried the same reproduction steps in 4.11.2 however and did reproduce the issue. Have you been able to reproduce this issue with anything other than the Survival Game Template?
Also, since you mentioned that all that needs to be done is to add the remaining files from that pull request, please be aware that they have nothing to do with this case and are of a different nature, as they deal with UMG directly. Adding those files would most likely not have any effect on this issue.