While reading through all the posts in this thread, this was going to be my suggestion. Glad you got to it.
The reason for it to have been my suggestion is that I have seen a bug in WUs that has still not been addressed by Bubble. I had a backend workflow, consuming a small amount of WUs which totaled around 1.8 WUs per day for an API call that was not necessary. I deleted the backend workflow, yet it still shows as running and consuming WUs every day. This is in development and when I look at the WUs it is in the Development.
This seems to be a bug that is causing things to be out of sync with the reality of the app setup. Unfortunately, I have not taken the time to investigate whether an app optimization run will actually delete the backend workflow or not in a similar fashion it does for reusable elements, data types and fields etc.
Again, this is a known bug that I have raised and gotten no resolution to, and I believe recalling other users reporting via forum of this bug previously.
Likely, the reason for the usage spike, obviously the fact of the bug is the real case, but why such a high usage, is because since deleting the reusable element, the source of the data search was likely unconstrained and therefore searching and returning all entries (as support pointed out) because despite having been deleted, it likely was not deleted from the page in the app it was originally placed on, so the ‘element not found’ notice was likely not visible, as the reusable element itself was placed either in a group not visible or a popup (so on preview can not see the ‘element not found’)…also, probably an issue with the issue tracker not picking up things as consistently as it should, so the ‘app wide’ alert of the deleted reusable element not found on a page was not shown in editor.
Please make sure you report this as a bug to support. I will be having to report again about my ‘deleted workflow’ still running and getting charged. The more users reporting about the buggy behavior around WUs the better and faster it will start to function appropriately all the time.