@MarinaRukavitsyna thanks for your proposal, but I can't share the site. Maybe you could advise something by my test's code.
First version of my test (sometimes failed, sometimes passed):
71 | async fillDocType (docTypeParam) {
72 | await t
73 | .click(this.docType)
> 74 | .click(this.dropdownMenu.find('li').withExactText(docTypeParam));
75 | }
Second version (same problem):
72 | async fillDocType (docTypeParam) {
73 | await t
74 | .click(this.docType)
> 75 | .expect(this.dropdownMenu.visible).ok('Menu is visible')
76 | .click(this.dropdownMenu.find('li').withExactText(docTypeParam));
77 | }
this.dropdownMenu = Selector('ul.dropdown-menu');
I understand that I don't need to use "expect" explicitly, but I thought it could help.