Each time I make a change the preview line becomes red and I have to render

Hi everyone. I am using adobe prmier pro cc 2017.

The problem is, every time I make some even minor change to the clip, the preview top line becomes red and the preview starts lagging.

To make the preview smooth again, I have to render every time, which takes forever. 

Is there any way to avoid or fix this?

Here are my computer and graphic card specs:

Thanky you in advance.