I haven’t been keeping up with the changes but I still use virtual devices for testing. Was there any recent change that affected virtual devices? I have migrated my account to the new app but my V1 hub is currently unplugged.
People have found the Virtual Switch with automation may cause the looping (switch on and off continuously), and suggested to switch the device driver from Virtual Switch to Simulated Switch in SmartThings IDE to resolve the issue. Not 100% sure if this was something you were looking for, but would be a good idea to take a look and switch them to Simulated switches.
Or if someone is having this as a new problem, it could be this: