Sequencer get freezing in UE 4.17

After edit one shot, i come back to master track ( my camera animation here), sequencer get freezing. In task manager, ram usage for UE 4.17 keep increasing and eat all my memory. Sometime, I right click in timeline and engine get crash too. Anyone have the same problem with me?

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Do you have a lot of keyframes? A lot of tracks? Is performance ok if you don’t go in and out of a shot?
What does your sequence look like? Just trying to get some ideas about what might be causing the problem.

not much, about 5 track. Performance is ok, i have 120fps on high setting. 1 sequence A have 5 little sequence about 20s each ( each one have one car go a little distance). But after i restart engine 5 times i shutdown my computer and go to sleep, and tomorrow it work fine