Steps to reproduce:
When I switch tabs using Cmd+<Number>, numbers 1..8 eight switch to respective 1st, 2nd, ..., 8th tab, but when I press Cmd+9, it only highlights the last tab as active, but the content remains of the previously active tab. When I press prev/next tab (cmd+shift+[, cmd+shift+]) it switches to the next/prev of the previously active tab, not the current one.
Seems to reproduce only with Vertical tabs, with horizontal works correctly (the last tab truly becomes active).
The last tab (e.g. 20th) should highlight as active and the content region should show the content of that tab.
Orion, OS version; hardware type:
Version 0.99.110-beta (WebKit 613.1.12)
macOS 11.5.2 (20G95)
Macbook Air M1 (8gb ram)