In T374230#10771849, @Silvan_WMDE wrote:

@Kirilloparma We have created and merged a patch that will hopefully fix the issue. It is due for deployment on Wednesday. Please do leave a comment here if it is solved or not, once a new Item type Property is created.

I'm patiently waiting for this problem to be resolved, but I'll be honest and say that it's getting really annoying as I not only can't finalize the property creation (I have to wait almost a whole day, see just a recent case https://www.wikidata.org/wiki/Property:P13504), but I can't even just edit anymore. My edits are now taking hours to complete too and it's a huge inconvenience to me. Do you know when this problem might be solved? I ask because the report was made since last year, and the problem has not disappeared at all. Perhaps we should temporarily stop creating properties with the item data type, since there is no solution yet? Also, why is there no prior warning anywhere (at least before creating a property) that you will encounter technical issues when creating a property with the item data type? Is it possible to do something like that?