I further examined the issue.
Rolled back the plugin to version 1.6.3 and the problem disappeared. My conclusion is that it is a bug introduced to version 1.6.4.
I have not looked at the source code but checked the cookies in both situations and noticed that …
YPMShowingLimitationDomain4463 and YPMShowingLimitationHomePage4463 are set with v 1.6.3 while with the v 1.6.4 only YPMShowingLimitationHomePage4463 is set.
I hope that helps.