Event tick hooked to a line trace and only one "cast to actor" node make my fps fall slowly to unplayable. Is there any alternative to fix this ?

[Everynone]

There are some strange things going on:

Even though you do have a reference variable. Looks like you do it often, accessing data pins from non-exec branches. Unsafe, potentially catastrophic.

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The cast is not to blame here. But you can use an interface instead. I’d look for issues elsewhere. You did not answer about log warning / errors.