Dragging for changing the length of a clip to be full on the timeline almost impossible on a long video

I have met this issue earlier, too. This time, I have a long video - almost five hours long. The project has 41 + 1 input clips. The timeline has three video tracks. One track has the video clips, one track is for an image and one is for a text. I want the text and image to be present during the whole video. So I started dragging the end of the clip. That worked up to some degree and then, stopped working.

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 21.04
Release:	21.04
Codename:	hirsute

Shotcut version 21.08.29

The application log's size is 40.6 MB. This is the end of the application log:

[Debug ] Function autosaveTask finished in 50 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9849708 KB
[Debug ] Function autosaveTask finished in 31 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9840324 KB
[Debug ] Function autosaveTask finished in 50 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9906376 KB
[Debug ] Function autosaveTask finished in 51 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9529996 KB
[Debug ] Function autosaveTask finished in 45 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9422928 KB
[Debug ] Function autosaveTask finished in 42 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9437332 KB
[Debug ] Function autosaveTask finished in 46 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0
[Info ] Util::isMemoryLow available RAM = 9415016 KB
[Debug ] Function autosaveTask finished in 29 ms.
[Debug ] Database::deleteOldThumbnails::lambda removing 0

Reproduce the issue in Shotcut 21.08.29 with a nearly five-hour project containing 41+1 input clips and three video tracks on Ubuntu 21.04. Start by investigating the timeline's clip-end dragging behavior for long projects and use the supplied application-log excerpt for context. Done means extending an image or text clip to the full video duration remains possible and reliable.