We have a situation where if we edit specific blocks, we see database cpu peaks and a non-responding admin UI 

In logs we see that a specific query peaks on the database and if we follow application insight trace logs (epi is run on an app service in azure) for one of the requests from the admin UI we see a burst of sql server requests and also requests to epifind which seems to run in sequence making the response back to the frontend real slow.

The block is used on multiple pages, also on pages which are children to parents which also contains the block. 

Below follod what we see in the browser Network trace (not all requests listed only those that has an abnormal response time):  

To trigger the requests we edit in a field (XHtmlString tinyMCE) of the block and put focus in another field then these request fires:

POST https://*host*/EPiServer/cms/Stores/contentversion/ 

Response takes 1.2 minute

Automatically the this request is fired:

POST https://*host*/EPiServer/cms/Stores/contentdata/1911_81792 

Response takes 1.2 minute

After these calls have returned the admin UI signals that "Publish" can be done. And we publish, then this request is made

POST https://*host*/EPiServer/cms/Stores/contentdata/1911_81792 

This Response takes at least > 1.2 minutes (company proxy time outs) 

Edit has been published though 

In database logs we see this. HMM I cant upload images. You have to take my word for it. We see spikes from a particular query:

INSERT INTO @Result 

    SELECT 

        tblContentLanguage.fkLanguageBranchID AS OwnerLanguageID, 

        NULL AS ReferencedLanguageID, 

        tblContent.pkID AS OwnerID, 

        tblContentLanguage.Name  As OwnerName, 

        tp.pkID AS ReferencedID, 

        tpl.Name AS ReferencedName, 

        2 AS ReferenceType 

    FROM 

        tblContent 

    INNER JOIN  

        tblContentLanguage ON tblContentLanguage.fkContentID=tblContent.pkID 

    INNER JOIN 

        tblContent AS tp ON tblContent.ArchiveContentGUID=tp.ContentGUID 

    INNER JOIN 

        tblContentLanguage AS tpl ON tpl.fkContentID=tp.pkID 

    WHERE 

        (tblContent.ArchiveContentGUID IN (SELECT PageGUID FROM @pages)) AND 

        tpl.fkLanguageBranchID=tp.fkMasterLanguageBranchID AND 

        tblContentLanguage.fkLanguageBranchID=tblContent.fkMasterLanguageBranchID 

But this never gives any results as if we zoom into this part:

INNER JOIN 

    tblContent AS tp ON tblContent.ArchiveContentGUID=tp.ContentGUID 

Looking at the actual values for all ArchiveContentGUID in the table they are all NULL and ContentGUID is never NULL. So, the join will as I understand sql queries :-p never return any results. 

Ialso if we follow what happens after the application recieves the request

POST https://*host*/EPiServer/cms/Stores/contentversion/   

(And possibly the other frontend requests mentioned above, have not checked) 

We see that an massive amounts of requests to the database are performed but also stuck in between all those request are requests to epifind in sequence so that all in all it takes a superlong time to respond to the frontend

Anyone knows what is going on?