I have had it on the default setting forever, and for some reason now it keeps putting me in hybrid, with the tree at the top. Also, whenever I put up a response and it loads, it just shows my reply, not the rest of the thread. I went to the User CP and checked the settings, and nothing has been changed. Thread mode is still set at linear oldest.

When I change it at the top right of the thread, it'll go linear for that page, but the next one will return to hybrid.

 

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