This problem is seen frequently on Jenkins for google compute engine plugin...

When we configure agent nodes as a cloud nodes ie. Manage Jenkins -> Manage nodes and clouds -> configure cloud
We configure Agent labels with gcp templates. The issue we are seeing from last few months that is Region, zone, template get wiped out, Result in agent are not spawning up and build get stuck
The workaround we are doing is that we re-configures templates again and save. 
But this issue creating bad impact for production based Jenkins.
Please check following details of Jenkins to have more clarity and please let me know if more information needed

Jenkins version: 2.232.1

Google Compute Engine Plugin: 4.3.9