Upgraded to 7.3.1 and get a NPE

After upgrading to 7.3.1, I am getting null pointer exception and my tests fail.
In my tests, i call some methods where i use native selenium commands.
So, at the start of each method i get the driver and end of the method I change it back, so i can continue using katalon commands in the actual test case…some thing like this:

public static void usingSeleniumMethods(){
WebDriver driver = DriverFactory.getWebDriver()
.
.
(some function to perform)
.
.
.

DriverFactory.changeWebDriver(driver)

}

This worked fine before, but after the katalon upgrade (also had to upgrade chrome driver for 7.3.1), i get java.lang.NullPointerException
Disabling the above driver switch in method made it work, but gave a java.lang.NullPointerException at the end of test case.

Does we still need to follow below link for switching between katalon and selenium?
https://docs.katalon.com/katalon-studio/docs/using_selenium_webdriver_katalon_studio.html#driverfactory

What if you get the driver but you do NOT change it back?

When I don’t change it back, all steps passes but gave a java.lang.NullPointerException at the end of test case

Temporary solution, i am able to get by for now by NOT change driver back. But I still cannot execute katalon commands once I am back on my test case. So, we probably need a fix or some workaround as long term solution

Thanks!