Solved Issue with stripped blank lines in editor

Hello, does anyone have an idea what could cause carriage returns (blank lines) in messages to be replaced with spaces when editing posts? This has been a problem on my forum before upgrading to Kunena 5.2.1, but the problem has become worse with the new editor because it further collapses these double or quadruple spaces down to a single space, making it impossible to quickly find and restore the blank lines.

I saw this problem when a user was pasting formatted text.  The editor re-formatted it, and in addition to removing the carriage returns, wrapped the links with the url tag which then made the links not links when the message was posted. So the pasted message just lookes like one huge run-on paragraph with a bunch of non-linking urls mixed in.

This was solved for the user by having them first click the "Source" button before pasting.  Not really solved as it should not be this complicated and you can't train every users, but it resolved the issue for that particular user.

Thanks for the response, however I believe my problem is a little deeper and would like to share some additional information in the hopes that someone can help me get to the bottom of it.

First, I made a test post. Afterward, it appeared correctly:
 
Next, I checked the database to see how it is stored:
 
Next, I tried editing the post. The editor showed both words on one line with a single space between.
So, I looked at the page source and found that the newlines had been replaced with spaces:
 
I found the template file for this page and edited the HTML directly to try to narrow the cause. The result is that newlines were replaced even when present in the template HTML itself:
 
Does anyone have an idea as to what could be causing the newlines to get replaced with spaces?

In your first post you've written that you had this error also before the upgrade to K5.2.1 Was this error already with Kunena 5.1 present? If yes, which editor (Wysiwyg or BBCode) have you used?

rich wrote: In your first post you've written that you had this error also before the upgrade to K5.2.1 Was this error already with Kunena 5.1 present? If yes, which editor (Wysiwyg or BBCode) have you used?

Thank you for your attention to that detail and for your response. The answer is yes, and with both editors...but:

We finally isolated the issue today and it turned out to be caused by a system plugin from "iubenda" that was replacing the newline characters. In the unlikely event that someone else runs across this problem with this particular plugin (versions 1.2.9 to 1.3.3 in my case), I would just add some additional info: it only happened when the iubenda plugin was configured with the "secondary" parsing engine. The fix was to add a "false" parameter to the two associated function calls to str_get_html(...) to disable replacement of \r\n characters.

Thanks to everyone who spent a thought on this problem. It was plaguing us for a while and very elusive.

We are now outside of Kunena scope, but in plugins it can be set context so by example if it's set context to com_content it will modify only articles from com_content and nothing else