Hi Fotis! I understand your answer but the uploads to the server work without problems, both in the Image tab "selecting image from the pc", and in the JCE image editor. The problem only appears when I select an image already uploaded to the server to be the main image of the article.
Regards

Thanks Fotis! We didnt see errors, only warnings:


THIS WARNINGS:
_ /media/system/jscore.js:1 window.submitform() is deprecated use Joomla.submitform() instead
window.submitform @ core.js?e262ddda6f4611e2e09b9f369afb247a:1
Joomla.submitbutton @ index.php?option=com_k2&view=item&cid=29613:245
onclick @ index.php?option=com_k2&view=item&cid=29613:393
index.php?option=com_k2&view=item&cid=29613:1

_ [DOM] Found 2 elements with non-unique id #K2ExtraField_2: (More info: goo.gl/9p2vKq) index.php?option=com_k2&view=item&cid=29613:1


AND THIS INFO:

_ VM626 jquery.min.js:2 [Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event. Consider marking event handler as 'passive' to make the page more responsive. See www.chromestatus.com/feature/5745543795965952

add @ VM626 jquery.min.js:2
a.event.add @ VM630 jquery-migrate.min.js:2
(anonymous) @ VM626 jquery.min.js:2
each @ VM626 jquery.min.js:2
each @ VM626 jquery.min.js:2
xe @ VM626 jquery.min.js:2
on @ VM626 jquery.min.js:2
(anonymous) @ VM628 elfinder.min.js:10
o @ VM628 elfinder.min.js:11
trigger @ VM628 elfinder.min.js:9
(anonymous) @ VM628 elfinder.min.js:11
u @ VM626 jquery.min.js:2
fireWith @ VM626 jquery.min.js:2
i.<computed> @ VM626 jquery.min.js:2
a @ VM628 elfinder.min.js:9
M @ VM628 elfinder.min.js:9
u @ VM626 jquery.min.js:2
fireWith @ VM626 jquery.min.js:2
C @ VM626 jquery.min.js:2
n @ VM626 jquery.min.js:2


___media/jui/js/ jquery.min.js?e262ddda6f4611e2e09b9f369afb247a:2 [Violation] 'readystatechange' handler took 186ms
[Violation] Forced reflow while executing JavaScript took 81ms
VM628 elfinder.min.js:10 [Violation] 'requestAnimationFrame' handler took 69ms
[Violation] Forced reflow while executing JavaScript took 32ms


__ VM626 jquery.min.js:2 [Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event. Consider marking event handler as 'passive' to make the page more responsive. See www.chromestatus.com/feature/5745543795965952
add @ VM626 jquery.min.js:2
a.event.add @ VM630 jquery-migrate.min.js:2
(anonymous) @ VM626 jquery.min.js:2
each @ VM626 jquery.min.js:2
each @ VM626 jquery.min.js:2
xe @ VM626 jquery.min.js:2
on @ VM626 jquery.min.js:2
(anonymous) @ VM628 elfinder.min.js:10
o @ VM628 elfinder.min.js:11
trigger @ VM628 elfinder.min.js:9
(anonymous) @ VM628 elfinder.min.js:11
u @ VM626 jquery.min.js:2
fireWith @ VM626 jquery.min.js:2
i.<computed> @ VM626 jquery.min.js:2
a @ VM628 elfinder.min.js:9
M @ VM628 elfinder.min.js:9
u @ VM626 jquery.min.js:2
fireWith @ VM626 jquery.min.js:2
C @ VM626 jquery.min.js:2
n @ VM626 jquery.min.js:2


__ jquery.min.js?e262ddda6f4611e2e09b9f369afb247a:2 [Violation] 'readystatechange' handler took 186ms
[Violation] Forced reflow while executing JavaScript took 81ms


__ VM628 elfinder.min.js:10 [Violation] 'requestAnimationFrame' handler took 69ms
[Violation] Forced reflow while executing JavaScript took 32ms

Fotis, I attached the video in this link:

Thanks!

I'm on 2.10.4, Fotis! Has it changed in the last week?

See in my second post #177589 >
UPDATE >> I updagrade to 2.10.4 and the error persist! Probed into php 7.2 and 7.3

OK I will do it! Thanks

I ask you: is it possible that your add some changes for everyone?

1/ In View>Item>tmpl > Change the image tag "summary" of the Twitter card to: "summary_large_image"? I have read that other users also requested it.

2/ In Administrator, mod k2 stats > the time is incorrect, it is "K2_DATE_FORMAT" (broked the hours and minutes) but it will be: "K2_DATE_FORMAT_LC2"

These are two changes that I always make manually every time I update k2 in my sites! ;)