It's not recommended to use Physics together with other non-physics behaviors, but it's possible if you do it with caution.
If you are using Platform or similar behavior to move an object, make sure that Physics behavior on this object is disabled. And when Physics is enabled, disable Platform. Don't move objects with enabled Physics using non-physics methods or by changing their position directly (like "Set X", "Move at angle").
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Pathfinding plugin doesn't work well in platformer games, it's better suited for top-down view. Making enemy AI in platformer can be a tricky task, you can search the forum for some examples, try these links:
construct.net/forum/construct-2/how-do-i-18/-how-do-i-frequently-asked-que-41236
scirra.com/store/royalty-free-game-templates/super-platformer-ai-2462