Internal Server Error while creating SharePoint Online Team Site

Today I bring a weird error, it has been hard to follow the error and reproduce it, but finally I have been able to solve it. The error was the following:

The user tries to create a SharePoint Team Site from the portal
The user selects a Team Site and starts to fill the parameters
The problem here, is that it stucks on the “Checking” action to verify if the site exists wether or not, and after a few moments it shows a message to exit from the creation site page. In case the user selects “Stays on this webpage” the system does nothing, but in case the user selects “Exit from this page” it automatically fires the following error:
500 Internal Server Error, a great error take into account that we are talking about SharePoint Online…

Things that I checked before finding a solution…

Check if the problem was reproduced with other navigators… I tested with IE, Edge, Chrome, Firefox and SAfari, all of them had the same behaviour.
Check if the client has configured a group to restrict the creation of O365 groups
Check if it happens with all the users, yes it happens
Check if it happens with global administrators, nop the GA were able to create the groups

After digging a lot, I decided to check the traces with Fiddler, after that I was able to see a kind of redirection in the traces, so I decided to go to the Home of SharePoint tenant https://domain.sharepoint.com and check the site collection features at that level.

I was reviewing which features were activated, in order to try to clarify what was the point of that error. After checking all the features, I decided to deactivate the feature “Limited-access user permission lockdown mode”

I remember that this feature gave me some problems in the past while I was involved in OnPremises projects were we were deploying anonymous portals, so I decided to deactivate the feature.

After deactivating the feature, I checked the creation of SharePoint Team Sites with the user that was giving me problems at the beginning…. and BAM! problem solved!! Wiiiiiii

So I wonder that this SharePoint Team Site Creation Page has something related with anonymous permissions or something like that. It has been a weird problem, but finally the mistery has been resolved.