I've had a similar problem and it was caused by this. I was experimenting and trying to create a custom module with several attempts and using numero 500000 (the default) and then tried 500001, 500002 etc for different experiments. Along the way, going into the danger zone and deleting various previous attempts. Basically that Danger Zone delete does not fully delete what was previously created. To clean up properly you need to use MySQLWorkbench to clean up remnants in at least these tables..
The next thing I would say is that it's a mistake to experiment with a numero like 500001, the last digit needs to be zero because a module does not use just one number it uses a block of numbers (something like 500000 to control reading privileges, 500001 for create/modify, 500002 for delete etc - but those actual values are not gospel, just from my poor recollection).
So what I'm saying is that, if you clean out and start over, for me it worked, but of course 500000 is not a safe number anyway if you plan to distribute.
Hope that helps-R
The next thing I would say is that it's a mistake to experiment with a numero like 500001, the last digit needs to be zero because a module does not use just one number it uses a block of numbers (something like 500000 to control reading privileges, 500001 for create/modify, 500002 for delete etc - but those actual values are not gospel, just from my poor recollection).
So what I'm saying is that, if you clean out and start over, for me it worked, but of course 500000 is not a safe number anyway if you plan to distribute.
Hope that helps-R