These are bugs with specific features. Like every other system. Chill out… I’m using Sequencer for years and it’s mostly just fine, also with lot of Spawnables. A lot of games have been shipped with it, it’s totally production-ready 
Although these bugs with event tracks are quite annoying and it should receive a bit of love…
BTW, “experimental” label in UE4 means a feature that’s so early that API constantly changes, there might many breaking changes with the next release. And usually, there’s no documentation provided. And it’s just label, changing a label for system because you find many issues with won’t change anything in the feature development
Simply, report every bug you have - with a proper repo. If the issue can’t be found in public issue database (although it doesn’t mean it wasn’t reported and added to db).