All too slow with IE and Microsof Edge

[alotnak]

Typing search string is very slow. Opening drop down is very slow. This is something to do with big amount of issues to be in dropdown.
How you have resolved this problem? Is there a simple way to fix this?
I red about virtual dropdowns, but no idea, what to do with them and how.
I thought we just switch the component to ngx-select, but it has it's own problems and seems to be slow, it too.