Every change in doctype or permission makes 503 for 10 minutes

Hi. I’m new at erpnext but every time I change a doctype or a permission erpnext hangs for some minutes with error http 503. After a while it came back working properly.

Is this a normal thing? If not, where can I see what’s is happening? Logs? I’m using v12 fully updated on Ubuntu 18.

Thanks!