This is correct and expected behavior for older plugins, they basically intentionally broke compatibility with a lot of the older plugins in 1.11, both on a source code and on a binary level. The plugins have to be updated for sourcemod 1.11+ in order to work.
I learned it early on when the 64-bit engine dropped and it almost killed my server to.
The only surprising thing to me is why you didn't notice this sooner, are you downloading new plugins from alliedmods or something?

Jetpack can be particular because valve changed how gravity works in the last update.

Ingame menu's are blocked by default unless they set cl_showpluginmessages and fix the font of those.

Remember when I said hosting on Windows with custom dll's is painful? Now you know.
Its very likely a signature mismatch issue, the signatures you need are not public because your windows dll won't have the same ones as anyone else. You'd probably need to hunt for them on your own which is a difficult task.