You might want to take a look at the logs in portals/_default/logs.

For debugging, you might increate the logging level.

The error seems to appear once in a while but every time in context of bad html:
- https://www.dnnsoftware.c...e/posts/threadpage/2 : old theme with tables.
- third party module not closing a div: https://github.com/dnnsof...Platform/issues/3407

One more thing: As your error points to cookies and you mention 9.8....I remembered an issue with cookies that was solved for 9.8.1: https://github.com/dnnsof...Platform/issues/4308

Thanks for your advice on the subject - I have been through the log files with a log4net setting of 'All' but apparently this type of Javascript error isn't registered at the backend level.
Since the pages are created using a template containing preembedded and empty Live Html modules it could be that some kind of 'bad html error' since the markup tends to somewhat complicated.
Another thing to mention regarding this issue is the fact that when adding a new module on a page deploying the errorprone template the module in question will not be visible before emptying the cache. So I guess updating dnn would be worthwhile

Some further investigation in this issue reveals that the problem arises, regardless of the chosen skin, but depends upon whether the page/tab in question has been added by means of apage template that was created with the option 'Include content' turned on.
That makes it three different factors having to be present in order to make the error occur:
Client Resource Management must be turned on
The page in question must visible in the menu
The page must be have been created from a dnn template utilizing the option 'Include content'

As mentioned earlier, this error appeared first time after upgrading to dnn 9.8 and I have seen in the changelog of the latter that a bug related to inserting af new module has been fixed as described in this url:
https://github.com/dnnsof...Platform/issues/4112
It isn't exactly the same error, but both relate to the utilization of cookies in order to insert a new module. The inserted module in my case always ends up in the default contentPane and becomes visible once the dnn server cache has been emptied.
I pretend the problem could be related to the state of the recycle bin as this one is rarely if ever emptied and contains hundreds of soft deleted tabs and modules since it tends to occur on tabs having a specific parent page

I have had a similar issue and it was also related to HTML errors in the content of the placed module.
I would try uisng an HTML validator on the page after you cleared the Cache to see if that might be the case.

Thanks, but I don't think it is a question of bad html within the module that I am trying to add to the page in question since the problem is not related to a specific module but rather to a specific state of the page upon which I try to add a new module.

At this time I have tried with two different modules a custom made and a commercial one, Live Tabs from Mandeeps, both turned out the same way.  But taking your advice I will try out with a couple of other commercial dnn modules like EasyDNNNews for instance and see whether that changes the procedure.

It can also be caused by a module that's already on the page

Thanks for making that suggestion,but I have just verified that any bad html in modules existing on the page cannot be the cause of this issue.

If I add a new page called SubPageA based on a specific template to a specific page called ParentPageX I can then add a new module to SubPageA without any problem, but if I add a new page called SubPageB to another parent page called ParentPageY the problem will be present. If I then move SubPageB to to ParentPageX the problem will disappear.

This seems to indicate that a condition related to the page tree is involved but I can't figure out how and why this could be. Perhaps a phantom parent page that throws an error whenever a reference has been made or an invalid character figuring in a parent page name?

 

Hi Timo - finally your suggestion regarding other module instances on the page helped me find a temporary workaround solution. Inspecting the values in the Tabmodules table for a tab provided with the problem in question - the dnn.modulemanager in edit node throwing errors at  dnn.dnnModuleDialog.apply and handleNewModuleFromCookie methods - I found that some of the existing modules had a value in the CacheMethod column of 'MemoryModuleCachingProvider'. Tabs without any dnn.modulemanager issues only had NULL values in this field.

So changing field values in the CacheMethod column in tabmodules table of the concerned tab from MemoryModuleCachingProvider to NULL solved the problem.
It works - which is fine - but it doesn't make that much sence. Why would a CacheMethod value of MemoryModuleCachingProvider be invalid?