rom time to time I am unable to create a new web app. It has been an ongoing issue since SP Foundation 2013, we've upgraded to SP 2016 earlier in the year and this problem is still here. 
As we add more web application sites, the problem seems to come up more often. The site doesn't get fully created on the server. There is a virtual directory without any contents.
We're tried adjusting the app pool timers as described in the URL below. It works sometimes, then months later when we try to create another web app it fails.
https://www.spguides.com/request-timed-out-sharepoint-web-application/
We've tried various timer settings from 300 - 4000, 1500, 9999 etc. Tried it on the default app pool and central admin pool. Rebooting the application server and database server doesn't seem to help.
Any suggestions is greatly appreciated
thanks