I tested with v12.0.0-dev2531949 (pro)
and if you switch off the pagination in the global settings...

1.) ...there's still unnecessary 'wasted' space above and below the picture (in the modal)
(as if the theme / CSS keeps the space free for the [in this case] none existing pagination)

2.) ...the first (in time) opened modal (after cleaning the joomla & browser cache) shows no right arrow, but using the right arrow on the keyboard still works (grouped pics or gallery).
As soon as you close the modal and open it again the right arrow is shown correctly.
(after cleaning the joomla & browser cache the game starts over / this error shows up again)


both issues are with theme classic and the new themes as well,
both issues occur only with switched off pagination.


see attached pictures:

I tested with v12.0.0-dev2532141
1.) and 2.) are fixed

but now I see a very delayed response (1 .. 2 seconds) on mobile devices
when opening a modal or switch back an force the picture
this was not the case with the J3 Version
(tested with chrome on android / tested with different devices)

J4 Version / very "slow":
24max.de/temp/Time-Lag__J4-beta.mp4

J3 Version (reacts quickly):
(same pictures / same resolution / same device / same internet connection)
24max.de/temp/J3-Version_works_quickly.mp4

even if all pics are in the browsers cache already and the viewport orientation is not changed (no recalculation is necessary),
it seems to me that something is "processed too much" (on every click) in java script (?)
but I'm not an expert ...

[As you may know: typically 70% of all website visitors access the website with a mobile device - and the trend is rising rapidly -> that's why I test it so intensively]

----
there were already some "processor load issues" some beta versions before regularlabs.com/forum/modals/49970-autom...4-dev-version#104897
but I belive that it was better already with the last several dev versions already (?) -> but not sure t.b.h

which real* devices and OS'es / browsers ?
*(not emulated ?)

not sure what you mean with "online environment" ?

yes,
at the moment I have only two (older) devices available / at hand:
(on both the same 'slow' behaviour)
# motorola Moto G7 / Display 2270x1080 / 4GB RAM / Android 10 / latest chrome browser -> www.gsmarena.com/motorola_moto_g7-9357.php
# Cat S42 / Display 1440x720 / 3GB RAM / Android 11 / latest chrome browser -> www.gsmarena.com/cat_s42-10029.php

[edit] I just made another Test with an Asus ROG phone 3 (Octa-core-CPU) -> www.gsmarena.com/asus_rog_phone_3-10296.php ,
Android 12 / latest chrome browser 108.0.5359.128
and the issue is still visible, but the delay-times are half than on the other two phones (ca. 1s instead of 2s), so I still believe that is a kind of "CPU-load" (or GPU-load?) issue (Java-script ?)




The videos were recorded with:

I once installed an additional template (framework) in this Joomla 4 test installation,
it is not active, but I think it did some caching of its own, when I tested it once, if I remember right...

maybe it can interfere with modals in a bad way ?
you may deinstall it completely if you want ("shaper_helixultimate – Standard") " www.joomshaper.com/helix "

can you tell what caused it?

will test it later ...

works now on my mobile devices 👍