Bridge will usually generate previews with the wrong size when "Generate Monitor-Size Previews" has been enabled (checked). I would guess that this bug has been present for a while.

The setting can be found here: Preferences -> Advanced -> Generate Monitor-Size Previews

On my system (see below), I have a monitor with a resolution of 2560 x 1440 pixels. When "Generate Monitor-Size Previews" is not checked, Bridge generates preview files with a pixel width of 2048 pixels in this cache folder (2048 seems to be the default size):

C:\Users\xxxx\AppData\Roaming\Adobe\Bridge\Cache\v36\1024...

Then, when checking "Generate Monitor-Size Previews", I see preview files with a width of 2560 pixels for new files, which may be the expected width (but see note below *).

However, with "Generate Monitor-Size Previews" still checked, I exit Bridge, then starts Bridge again, then I double check that "Generate Monitor-Size Previews" is still set in Preferences (which it is). I then let Bridge generate new previews.

=> Now I notice that even if "Generate Monitor-Size Previews" is checked, Bridge reverts back to generating previews with a width of 2048 pixels!

=> It turns out that in order to get Bridge to generate the "correct" preview size (2560 pixels in my case), I must, each time I start Bridge, go into Preferences and then turn "Generate Monitor-Size Previews" off and then on again to get the correct preview size for new images. The preference setting only takes effect while Bridge keeps running.

This is maybe a minor bug (the previews gets a little blurry though), but one may wonder if this "ignoring" of preference settings may also happen for other settings?

*) Note:
I note that for 3:2 images the preview files are 2560 x 1707 pixels in size when "Generate Monitor-Size Previews" is working. This means that the preview files have a height that is larger than the height of my 16:9 monitor (2560 x 1440 pixels). I guess that when checking "Generate Monitor-Size Previews" the 3:2 preview files on my system really should have been something like 2160 x 1440 pixels?

Before running the tests described above, I did the following:

1) Deleted the Bridge cache (Bridge then automatically builds a new empty cache when started).
2) Cleared Bridge preferences (Ctrl+Alt+Shift on startup)
3) Uninstall Bridge
4) Install the latest version of Bridge (14.0.4.222)

System details:

Adobe Bridge Version: 14.0.4.222

Windows: Windows 11 Pro 64-bit
Version: 23H2 (Version 10.0.22631.3447)
OS build: 22631.3447

NVIDIA GeForce RTX 2060
NVIDIA Studio Driver, version: 552.22 Release date: 04/16/2024

CPU: AMD Ryzen 9 5950X
RAM: 64 GB

Monitor: Eizo CG2730 - 2560x1440 - Wide Gamut - Xrite i1 Display