SUMMARY
I've noticed several issues whilst using Dialog box with my Qt applications e.g. Chromium, Audacious.

STEPS TO REPRODUCE
1. Open Chromium
2. Go to any Rapidgator-kind of site and try to download any file
3. When Dialog box pops up, rename the default filename and change the path to any different location on your disk
4. Wait for a few seconds and multiple crashes (Segfaults) may appear

Observed issue whilst using Audacious has been already described here:
https://bugs.kde.org/show_bug.cgi?id=428181#c4

OBSERVED RESULT

Application: kdeinit5 (kdeinit5), signal: Segmentation fault

[KCrash Handler]
#4  0x00007f4d261ed566 in __memmove_avx_unaligned_erms () from /usr/lib/libc.so.6
#5  0x00007f4d270be492 in ?? () from /usr/lib/qt/plugins/kf5/kio/thumbnail.so
#6  0x00007f4d22b536df in KIO::SlaveBase::dispatch(int, QByteArray const&) () from /usr/lib/libKF5KIOCore.so.5
#7  0x00007f4d22b54006 in KIO::SlaveBase::dispatchLoop() () from /usr/lib/libKF5KIOCore.so.5
#8  0x00007f4d270bc026 in kdemain () from /usr/lib/qt/plugins/kf5/kio/thumbnail.so
#9  0x000055cdd53cc5bd in ?? ()
#10 0x000055cdd53cda59 in ?? ()
#11 0x000055cdd53ce237 in ?? ()
#12 0x000055cdd53c9b54 in ?? ()
#13 0x00007f4d260b0b25 in __libc_start_main () from /usr/lib/libc.so.6
#14 0x000055cdd53ca6be in ?? ()
[Inferior 1 (process 3067) detached]


Application: KDialog (kdialog), signal: Segmentation fault

[KCrash Handler]
#4  0x00007ff3cbccb566 in __memmove_avx_unaligned_erms () from /usr/lib/libc.so.6
#5  0x00007ff3cc772917 in QImage::copy(QRect const&) const () from /usr/lib/libQt5Gui.so.5
#6  0x00007ff3c76704b2 in ?? () from /usr/lib/libKF5KIOWidgets.so.5
#7  0x00007ff3cc1fe996 in ?? () from /usr/lib/libQt5Core.so.5
#8  0x00007ff3cd615735 in KIO::TransferJob::data(KIO::Job*, QByteArray const&) () from /usr/lib/libKF5KIOCore.so.5
#9  0x00007ff3cc1fe996 in ?? () from /usr/lib/libQt5Core.so.5
#10 0x00007ff3cd5f1ac3 in KIO::SlaveInterface::data(QByteArray const&) () from /usr/lib/libKF5KIOCore.so.5
#11 0x00007ff3cd5f3f7d in KIO::SlaveInterface::dispatch(int, QByteArray const&) () from /usr/lib/libKF5KIOCore.so.5
#12 0x00007ff3cd5f228a in KIO::SlaveInterface::dispatch() () from /usr/lib/libKF5KIOCore.so.5
#13 0x00007ff3cd5f5d8b in KIO::Slave::gotInput() () from /usr/lib/libKF5KIOCore.so.5
#14 0x00007ff3cc1fe996 in ?? () from /usr/lib/libQt5Core.so.5
#15 0x00007ff3cc1f4142 in QObject::event(QEvent*) () from /usr/lib/libQt5Core.so.5
#16 0x00007ff3cce12762 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQt5Widgets.so.5
#17 0x00007ff3cc1c763a in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib/libQt5Core.so.5
#18 0x00007ff3cc1ca133 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/lib/libQt5Core.so.5
#19 0x00007ff3cc220b04 in ?? () from /usr/lib/libQt5Core.so.5
#20 0x00007ff3ca92202c in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#21 0x00007ff3ca975b59 in ?? () from /usr/lib/libglib-2.0.so.0
#22 0x00007ff3ca91f781 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#23 0x00007ff3cc220141 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#24 0x00007ff3cc1c5f9c in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#25 0x00007ff3cd01657a in QDialog::exec() () from /usr/lib/libQt5Widgets.so.5
#26 0x00007ff3cd0164b6 in QDialog::exec() () from /usr/lib/libQt5Widgets.so.5
#27 0x000055a6947837ae in ?? ()
#28 0x00007ff3cbb8eb25 in __libc_start_main () from /usr/lib/libc.so.6
#29 0x000055a69478569e in _start ()
[Inferior 1 (process 3675) detached]

EXPECTED RESULT
I've never experienced this error before.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.4.112-1-MANJARO
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.81.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION