Images with '300x250' in the name dont appear in image library thumbnails

[neilosj]

Uploading any image with the exact phrase '300x250' in the name doesn't display the thumbnail in the media library.
Viewing the inspector element, the thumbnail doesn't load but viewing teh image directly does show it exists.
I have tested this on versions 4.4.18 to 4.9.9 and the same behaviour exists.
Calling the images something different does display. E.G.
301x250
299x250
3000x2500
3x00250
30x0250
3002x50

[neilosj]

anything with 300x250 image name error

[Presskopp]

Welcome to Trac!

What if you use a standard theme and no plugins?
What if you use the latest WP version with a standard theme and no plugins?

[neilosj]

Hi,
Same results.
I installed 5.1.1, updated everything that came as standard;
Plugins
Akismet
Hello Doly
inSite for WP
Jetpack
WP Control
WP-Cron control
None of these are activated.

Themes;
2016
2017
2019 - Active

I installed it primarily to upload two images to test, and it is the same.
300x250.jpg - no thumbnail in the Media library, though image is available.
3000x2500.jog - thumbnail appears in media library.
These are the same image, just copied and pasted and name changed.

[Presskopp]

I'm unable to reproduce this.

Screenshot from WordPress 5.1.1, TwentyNineteen, no Plugin active. Doesn't look like a core bug. You can still comment if you have some more details like from your error log.