Oh no! Sorry to hear that, Martin.
It looks like you indicated having carried out some testing already by deactivating other plugins – but I wonder if you could do that and switch to a default theme, too:
theeventscalendar.com/knowledgebase/testing-for-conflicts
The reason I ask is most users are not reporting this issue and it does have the hallmarks of a conflict. Alternatively, or additionally, if you are comfortable doing so can you try using your browser dev tools to check if there might be a Javascript-level error?
Thanks!