Hi Chetan thanks for posting and I'm sorry for any trouble. What you can do to quickly fix it is select the diagram right click and select ungroup. Then you can manually adjust the lines that aren't straight. But please note that once you ungroup the diagram you will be unable to edit the markup for that particular sequence anymore so be sure to have the structure the way you wish. Though you can always use your same markup pasted above to generate a new one if needed.

If this doesn't help or you continue to experience trouble please submit a support ticket by emailing support@lucidchart.com and we can take a closer look!

I can try the workaround but it is bit messy and would prefer the diagram generated by markup itself should be correct. Is there any existing ticket to fix the current problamatic behaviour?

Hi Chetan yes this is an issue that has been filed with our product team and they are looking into it. The activation boxes are what is causing the ridges in the lines if they are removed the lines will straighten. I apologize for any inconvenience this causes-- in the meantime as a workaround I recommend manually adjusting them so you have your desired layout.