Yeah that error (Wrong datatype … post-template.php on line 1039) is a known problem – but we’re confident it has been resolved as of The Events Calendar 3.0, which is currently in testing.
Can I ask you to try flushing the permalinks (visit Settings > Permalinks – you don’t actually have to change anything though) and see if that impacts at all. Failing that, can you try changing the events/single events slug settings found in Events > Settings > General? (And again, flush the permalinks after doing so).
Does that help at all?