[Domain Mapping] activity updates not working when domain mapping enabled, strange

Dear team, after the latest updates, WP 4.9.6. (multisite), BP3.0 and Domain Mapping i am noticing a very strange behavior on my site. first i thought the latest update on the Kleo theme causes these issues but after i night full of crosstesting all the plugins i noticed that the latest version of the wpmu domain mapping plugin causes the following effect that the activity feed did not allow any updates and "load more" clicks, the update button simply stopped working. also the buddypress login widget ran into an 502 bad gateway error, very strange.
After a lot of testing, and this is replicable, activity steam update button is not working unter https when the domain mapping plugin is activated, but will work via http.if i deactivate the domain mapping plugin it works again under https and http. i am not sure, if it is an cookie or https issue, but it worked fine with the domain mapping plugin version before.
maybe you can check? playing with different domain mapping plugin settings (force https on/off etc.) makes no difference.
may i kindly ask for help? this issue is replicable on my staging site.
tnx, eric