In the new 1.17.1-fabric0.36.1-1.2.2, the rendering of lower tabs is quite interesting, they actually work if you click on them, it's just that they're in the wrong place.

In the older 1.17.1-fabric0.36.1-1.2.1. this issue doesn't exist.

Thanks for noticing this! Should be fixed in version 1.3 which I just published. If not, feel free to reopen.