Hi Pat,

This is actually a known issue where the fix has been applied in our repository and will be included in our incoming release.
I've replace the file below and rename the existing file with '_bak' appends(incase you've make some changes in the file):

.../components/com_easydiscuss/views/post/view.ajax.php
.../components/com_easydiscuss/themes/wireframe/post/default.js
.../components/com_easydiscuss/themes/wireframe/post/default.actions.php
.../components/com_easydiscuss/controllers/posts.php

and I've add these language string in the '.../language/en-GB/en-GB.com_easydiscuss.ini' file:

COM_EASYDISCUSS_POST_RESOLVED_TITLE="Mark resolve"
COM_EASYDISCUSS_POST_RESOLVED_DESC="Do you want to mark this thread as resolve?"
COM_EASYDISCUSS_BUTTON_YES_MARK_POST_RESOLVED="Resolve"

COM_EASYDISCUSS_POST_UNRESOLVED_TITLE="Mark unresolve"
COM_EASYDISCUSS_POST_UNRESOLVED_DESC="Do you want to mark this thread as unresolve?"
COM_EASYDISCUSS_BUTTON_YES_MARK_POST_UNRESOLVED="Unresolve"

Can you give it another try?

When "Mark Resolved" or "Mark Unresolved" is pressed, "Internal Server Error" appears.

Sorry about that Pat, seems like some of the file I'm forgot to copy it out.
I've copy these file below:
.../components/com_easydiscuss/themes/wireframe/post/dialogs/mark.post.resolve.php
.../components/com_easydiscuss/themes/wireframe/post/dialogs/mark.post.unresolve.php
Can you try it again and see how it goes?

Hi,
thank you for your help! It works now!

I noticed that sometimes popup window appears twice, if "Accept as answer" button is pressed.

Hi Pat,

I've try to replicate this issue in your site click multiple time of the 'Accept as answer' button, seems I cannot reproduce it: https://www.screencast.com/t/Z1QhHjJE67H

Click on the 'Accept as answer' ('Zaakceptuj odpowiedź') button in the replies section and then click 'Yes, Accept As Answer' ('Tak, to właściwa odpowiedź').

Sorry for replicate it wrongly Pat. I've tried to reproduce the issue as per your steps given above (somehow i didn't see the Zaakceptuj odpowiedź button in the reply section.
I believe I've replicate this issue correctly now, yes? https://www.screencast.com/t/3cQHWou7DIlM
Seems like I'm still unable to reproduce the popup appear twice.

You have administrator privileges, so you see a slightly different interface. The user sees the Zaakceptuj odpowiedź button when he or she is the author of the question.

I replicate this behavior in IE and Chrome but I can't do this in Firefox. Look here

I've noticed that it's easier to call this bug when the browser is refreshed before.

Thanks for the video attached Pat, I've try to replicate this issue in Chrome and Internet Explorer for some time now, refresh the page before click on the button and any possible way to replicate this , seems like I'm still unable to reproduce the issue https://www.screencast.com/t/jUpNKb1jwwIW

I will keep watching it. Strange is that this only happens with this popup.

Please do not worry about it. If there are new facts I will let you know. Thank you for trying to understand the problem.

Thanks for your understanding Pat, sure! keep us update when you encounter the issue with apparent steps, so we can find the root issue